               #CEJ ,,BC
     ,,ON ,,! ,,GAIT ,,( ,,ANIMALS
               0,>I/OTLE
       TRANSLAT$ BY ;,A4 ,S4 ,L4
               ,F>QUH>SON
    ,TRANSLAT$ 6,GRADE ,,II ,BRL 0,MIKE
    ,KEI?LEY
                   #A
  ,WE H N[ 63SID] ! "PS : >E USE;L
6ANIMALS = MOVE;T 9 PLACE 7LOCOMO;N72
F/1 :Y EA* "P IS S* Z X IS & 6:AT 5D !Y
POSSESS !M2 & SECOND1 ! DI6];ES 2T ^!
"PS BO? 9 "O &! SAME CR1TURE1 & AG
0-P>ISON (! "PS ( CR1TURES ( DI6]5T
SPECIES ) "O ANO!R4 ,F/ !N LET U LAY D[N
H[ _M "QS WE H 63SID]4
  ,! F/ IS :AT >E ! FEWE/ PO9TS ( MO;N
NEC 6ANIMAL PROGRES.N1 ! SECOND :Y
SANGU9E\S ANIMALS H F\R PO9TS & N M1 B
BLOOD.S ANIMALS M ?AN F\R1 & G5],Y :Y "S
ANIMALS >E FOOT.S1 O!RS BIP$S1 O!RS
QUADRUP$S1 O!RS POLYPODS1 & :Y ALL H AN
EV5 NUMB] ( FEET1 IF !Y H FEET AT ALL2
:Y 9 F9E ! PO9TS ON : PROGRES.N DEP5DS
>E EV5 9 NUMB]4
  ,NEXT1 :Y >E MAN & BIRD BIP$S1 B FI%
FOOT.S2 & :Y D MAN & BIRD1 ?\< BO?
BIP$S1 H AN OPPOSITE CURVATURE (! LEGS4
,= MAN B5DS 8 LEGS 3VEXLY1 A BIRD HAS 8
B5T 3CAVELY2 AG1 MAN B5DS 8 >MS & LEGS 9
OPPOSITE DIREC;NS1 = HE HAS 8 >MS B5T
3VEXLY1 B 8 LEGS 3CAVELY4 ,&A VIVIP>\S
QUADRUP$ B5DS 8 LIMBS 9 OPPOSITE
DIREC;NS 6A MAN'S1 & 9 OPPOSITE DIREC;NS
6"O ANO!R2 = HE HAS 8 =ELEGS B5T 3VEXLY1
8 H9D LEGS 3CAVELY4 ,AG1 QUADRUP$S : >E
N VIVIP>\S B OVIP>\S H A PECULI>
CURVATURE (! LIMBS LAT],Y AWAY F ! BODY4
,AG1 :Y D QUADRUP$S MOVE _! LEGS CRISS-
CROSS8
  ,WE H 6EXAM9E ! R1SONS = ALL ^! FACTS1
& O!RS COGNATE 6!M2 T ! FACTS >E S* IS
CLE> F \R ,NATURAL ,HI/ORY1 WE H N[ 6ASK
R1SONS =! FACTS4

                   #B
  ,AT ! 2G9N+ (! 9QUIRY WE M/ PO/ULATE !
PR9CIPLES WE >E A3U/OM$ 3/ANTLY 6USE =
\R SCI5TIFIC 9VE/IG,N ( NATURE1 T IS WE
M/ TAKE = GRANT$ PR9CIPLES ( ? UNIV]SAL
"* : APPE> 9 ALL ,NATURE'S "W4 ,( ^! "O
IS T ,NATURE CR1TES NO?+ )\T A PURPOSE1
B ALW ! BE/ POSSI# 9 EA* K9D ( LIV+
CR1TURE 0REF];E 6XS ESS5TIAL 3/ITU;N4
,ACLY IF "O WAY IS BETT] ?AN ANO!R T IS
! WAY ( ,NATURE4 ,NEXT WE M/ TAKE =
GRANT$ ! DI6]5T SPECIES ( DIM5.NS : 9"H
9 V>I\S ?+S2 ( ^! "! >E ?REE PAIRS ( TWO
EA*1 SUP]IOR & 9F]IOR1 2F & 2H1 6! "R &
6! LEFT4 ,FUR!R WE M/ ASSUME T !
ORIG9ALS ( MOVE;TS 9 PLACE >E ?RU/S &
PULLS4 7,^! >E ! ESS5TIAL PLACE-MOVE;TS1
X IS ONLY A3ID5T,Y T :AT IS C>RI$ 0ANO!R
IS MOV$2 X IS N ?"\ 6MOVE XF1 B 6BE MOV$
0"S?+ ELSE47

                   #C
  ,AF ^! PRELIM9>IES1 WE G ON 6! NEXT
"QS 9 ORD]4 ,N[ ( ANIMALS : *ANGE _!
POSI;N "S MOVE )! :OLE BODY AT ONCE1 =
EXAMPLE JUMP+ ANIMALS1 O!RS MOVE "O "P
F/ & !N ! O!R1 = EXAMPLE WALK+ 7& RUNN+7
ANIMALS4 ,9 BO? ^! *ANGES ! MOV+ CR1TURE
ALW *ANGES XS POSI;N 0PRESS+ AG/ :AT
LIES 2L X4 ,ACLY IF :AT IS 2L GIVES WAY
TOO QKLY = T : IS MOV+ ^U X 6L1N AG/ X1
OR IF X AF=DS NO RESI/.E AT ALL 6:AT IS
MOV+1 ! LATT] C ( XF E6ECT NO MOVE;T ^U
X4 ,= AN ANIMAL : JUMPS MAKES XS JUMP
BO? 0L1N+ AG/ XS [N UPP] "P & AL AG/ :AT
IS 2N XS FEET2 = AT ! JO9TS ! "PS D 9 A
S5SE L1N ^U "O ANO!R1 & 9 G5]AL T :
PU%ES D[N L1NS ^U :AT IS PU%$ D[N4 ,T IS
:Y A?LETES JUMP FUR!R ) WEI<TS 9 _! H&S
?AN )\T1 & RUNN]S RUN FA/] IF !Y SW+ _!
>MS2 "! IS 9 EXT5D+ ! >MS A K9D ( L1N+
AG/ ! H&S & WRI/S4 ,9 ALL CASES !N T :
MOVES MAKES XS *ANGE ( POSI;N 0! USE (
AT L1/ TWO "PS (! BODY2 "O "P S 6SP1K
SQUEEZES1 ! O!R IS SQUEEZ$2 =! "P T IS /
IS SQUEEZ$ Z X HAS 6C>RY ! WEI<T1 ! "P T
IS LIFT$ /RA9S AG/ T : C>RIES ! WEI<T4
,X FOLL[S !N T NO?+ )\T "PS C MOVE XF 9
? WAY1 = X HAS N 9 X ! 4T9C;N (! "P : IS
PASSIVE & T : IS ACTIVE4
                   #D
  ,AG1 ! B.D>IES 0: LIV+ 2+S >E NATUR,Y
DET]M9$ >E SIX 9 NUMB]1 SUP]IOR &
9F]IOR1 2F & 2H1 "R & LEFT4 ,( ^! ALL
LIV+ 2+S H A SUP]IOR & AN 9F]IOR "P2 =
SUP]IOR & 9F]IOR IS 9 PLANTS TOO1 N ONLY
9 ANIMALS4 ,& ? 4T9C;N IS "O ( FUNC;N1 N
M]ELY ( POSI;N RELATIVELY 6\R E>? &! SKY
ABV \R H1DS4 ,! SUP]IOR IS T F : FL[S 9
EA* K9D ! 4TRIBU;N ( NUTRI;T &! PROCESS
( GR[?2 ! 9F]IOR IS T 6: ! PROCESS FL[S
& 9 : X 5DS4 ,"O IS A />T+-PO9T1 ! O!R
AN 5D1 &! />T+-PO9T IS ! SUP]IOR4 ,& YET
X MI<T 2 ?"\ T 9 ! CASE ( PLANTS AT L1/
! 9F]IOR IS R ! APPROPRIATE />T+-PO9T1 =
9 !M ! SUP]IOR & 9F]IOR >E 9 POSI;N O!R
?AN 9 ANIMALS4 ,/ !Y >E SIMIL>LY SITUAT$
F ! PO9T ( VIEW ( FUNC;N1 ?\< N 9 _!
POSI;N RELATIVELY 6! UNIV]SE4 ,! ROOTS
>E ! SUP]IOR "P (A PLANT1 = F !M !
NUTRI;T IS 4TRIBUT$ 6! GR[+ MEMB]S1 &A
PLANT TAKES X ) XS ROOTS Z AN ANIMAL
DOES ) XS M\?4
  ,?+S T >E N ONLY ALIVE B >E ANIMALS H
BO? A FRONT &A BACK1 2C !Y ALL H S5SE1 &
FRONT & BACK >E 4T+UI%$ 0REF];E 6S5SE4
,! FRONT IS ! "P 9 : S5SE IS 9NATE1 &
:;E EA* ?+ GETS XS S5S,NS1 ! OPPOSITE
"PS >E ! BACK4
  ,ALL ANIMALS : P>TAKE N ONLY 9 S5SE1 B
>E A# ( !MVS 6MAKE A *ANGE ( PLACE1 H A
FUR!R 4T9C;N ( LEFT & "R 2SS ^? ALR
ENUM]AT$2 L ! =M] ^! >E 4T9C;NS ( FUNC;N
& N ( POSI;N4 ,! "R IS T F : *ANGE (
POSI;N NATUR,Y 2G9S1 ! OPPOSITE :
NATUR,Y DEP5DS ^U ? IS ! LEFT4
  ,? 4T9C;N 7( "R & LEFT7 IS M >TICULATE
& DETAIL$ 9 "S ?AN 9 O!RS4 ,= ANIMALS :
MAKE ! A=ESD *ANGE 7( PLACE7 0! HELP (
ORGANIZ$ "PS 7,I M1N FEET = EXAMPLE1 OR
W+S OR SIMIL> ORGANS7 H ! LEFT & "R
4T+UI%$ 9 GRT] DETAIL1 :ILE ^? : >E N
DI6]5TIAT$ 96S* "PS1 B MAKE ! DI6]5TI,N
9 ! BODY XF & S PROGRESS1 L "S FOOT.S
ANIMALS 7= EXAMPLE SNAKES & CAT]PILL>S
AF _! K9D1 & 2SS :AT M5 CALL E>?-WORMS71
ALL ^! H ! 4T9C;N SPOK5 (1 AL? X IS N
MADE S MANIFE/ 6U4 ,T ! 2G9N+ ( MOVE;T
IS ON ! "R IS 9DICAT$ 0! FACT T ALL M5
C>RY BURD5S ON ! LEFT %\LD]2 9 ? WAY !Y
SET FREE ! SIDE : 9ITIATES MOVE;T & 5A#
! SIDE : BE>S ! WEI<T 6BE MOV$4 ,& S M5
HOP EASI] ON ! LEFT LEG2 =! NATURE (! "R
IS 69ITIATE MOVE;T1 T (! LEFT 6BE MOV$4
,! BURD5 !N M/ RE/ ON ! SIDE : IS 6BE
MOV$1 N ON T : IS GO+ 6CAUSE MOVE;T1 &
IF X 2 SET ON ! MOV+ SIDE1 : IS !
ORIG9AL ( MOVE;T1 X W EI N 2 MOV$ AT ALL
OR ) M LAB\R4 ,ANO!R 9DIC,N T ! "R IS !
S\RCE ( MOVE;T IS ! WAY WE PUT \R FEET
=W>D2 ALL M5 L1D (F )! LEFT1 & AF /&+ /
PREF] 6PUT ! LEFT FOOT =W>D1 UN.S "S?+
HAPP5S 6PREV5T X4 ,! R1SON IS T _!
MOVE;T -ES F ! LEG !Y /EP (F1 N F ! "O
PUT =W>D4 ,AG1 M5 GU>D !MVS ) _! "R4 ,&
? IS ! R1SON :Y ! "R IS ! SAME 9 ALL1 =
T F : MO;N 2G9S IS ! SAME = ALL1 & HAS
XS NATURAL POSI;N 9 ! SAME PLACE1 &= ?
R1SON ! SPIRAL-%AP$ ,TE/AC1NS H _! %ELLS
ON ! "R1 = !Y D N MOVE 9 ! DIREC;N (!
SPIRE1 B ALL G =W>D 9 ! DIREC;N OPPOSITE
6! SPIRE4 ,EXAMPLES >E ! MUREX &! C]YX4
,Z ALL ANIMALS !N />T MOVE;T F ! "R1 &!
"R MOVES 9 ! SAME DIREC;N Z ! :OLE1 X IS
NEC = ALL 6BE ALIKE "R-H&$4 ,& MAN HAS !
LEFT LIMBS DETA*$ M ?AN ANY O!R ANIMAL
2C HE IS NATURAL 9 A HI<] DEGREE ?AN !
O!R ANIMALS2 N[ ! "R IS NATUR,Y BO?
BETT] ?AN ! LEFT & SEP>ATE F X1 & S 9
MAN ! "R IS M ESPECI,Y ! "R1 M DEXTR\S T
IS1 ?AN 9 O!R ANIMALS4 ,! "R !N 2+
DI6]5TIAT$ X IS ONLY R1SONA# T 9 MAN !
LEFT %D 2 MO/ MOVA#1 & MO/ DETA*$4 ,9
MAN1 TOO1 ! O!R />T+-PO9TS >E F.D MO/
NATUR,Y & CLE>LY 4T9CT1 ! SUP]IOR "P T
IS &! FRONT4
                   #E
  ,ANIMALS :1 L M5 & BIRDS1 H ! SUP]IOR
"P 4T+UI%$ F ! FRONT >E TWO-FOOT$
7BIP$74 ,9 !M1 (! F\R PO9TS ( MO;N1 TWO
>E W+S 9 ! "O1 H&S & >MS 9 ! O!R4
,ANIMALS : H ! SUP]IOR &! FRONT "PS
ID5TIC,Y SITUAT$ >E F\R-FOOT$1 _M-FOOT$1
OR FOOT.S 7QUADRUP$1 POLYPOD1 LIMB.S74
,I USE ! T]M FOOT =A MEMB] EMPLOY$ =
MOVE;T 9 PLACE 3NECT$ )A PO9T ON ! GR.D1
=! FEET APPE> 6H GOT _! "N F ! GR.D "U
\R FEET4
  ,"S ANIMALS1 TOO1 H ! FRONT & BACK "PS
ID5TIC,Y SITUAT$1 = EXAMPLE1
,CEPHALOPODS 7MOLLUSCS7 & SPIRAL-%AP$
,TE/AC1NS1 & ^! WE H 4CUSS$ ELSE": 9
ANO!R 3NEXION4
  ,N[ "! IS 9 PLACE A SUP]IOR1 AN
9T]M$IATE1 & AN 9F]IOR2 9 RESPECT 6PLACE
BIP$S H _! SUP]IOR "P CORRESPOND+ 6! "P
(! UNIV]SE2 QUADRUP$S1 POLYPODS1 &
FOOT.S ANIMALS 6! 9T]M$IATE "P1 & PLANTS
6! 9F]IOR4 ,! R1SON IS T ^! H NO P[] (
LOCOMO;N1 &! SUP]IOR "P IS DET]M9$
RELATIVELY 6! NUTRI;T1 & _! NUTRI;T IS F
! E>?4 ,QUADRUP$S1 POLYPODS1 & FOOT.S
ANIMALS AG H _! SUP]IOR "P CORRESPOND+
6! 9T]M$IATE1 2C !Y >E N ERECT4 ,BIP$S H
_!S CORRESPOND+ 6! SUP]IOR "P (! UNIV]SE
2C !Y >E ERECT1 &( BIP$S1 MAN P>
EXCELL;E2 = MAN IS ! MO/ NATURAL (
BIP$S4 ,& X IS R1SONA# =! />T+ PO9TS 6BE
9 ^! "PS2 =! />T+-PO9T IS HON\RA#1 &!
SUP]IOR IS M HON\RA# ?AN ! 9F]IOR1 !
FRONT ?AN ! BACK1 &! "R ?AN ! LEFT4 ,OR
WE MAY REV]SE ! >GU;T & SAY Q WELL T ^!
"PS >E M HON\RA# ?AN _! OPPOSITES J 2C !
/>T+-PO9TS >E 9 !M4
                   #F
  ,! ABV 4CUS.N HAS MADE X CLE> T !
ORIG9AL ( MOVE;T IS 9 ! "PS ON ! "R4 ,N[
E 3T9U\S :OLE1 "O "P ( : IS MOV$ :ILE !
O!R REMA9S AT RE/ M/1 9 ORD] 6BE A#
6MOVE Z A :OLE :ILE "O "P /&S /1 H 9 !
PLACE ": BO? "PS H OPPOS$ MOVE;TS "S
-MON "P : 3NECTS ! MOV+ "PS ) "O ANO!R4
,FUR!R 9 ? -MON "P ! ORIG9AL (! MO;N 7&
SIMIL>LY (! ABS;E ( MO;N7 ( EA* (! "PS
M/ LIE4
  ,CLE>LY !N IF ANY (! OPPOSITE PAIRS (
"PS 7"R & LEFT1 T IS1 SUP]IOR & 9F]IOR1
2F & 2H7 H A MOVE;T ( _! [N1 EA* ( !M
HAS = -MON ORIG9AL ( XS MOVE;TS !
JUNCTURE (! "PS 9 "Q4
  ,N[ 2F & 2H >E N 4T9C;NS RELATIVELY 6T
: SETS UP XS [N MO;N1 2C 9 NATURE NO?+
HAS A MOVE;T BACKW>DS1 NOR HAS A MOV+
ANIMAL ANY DIVI.N ":BY X MAY MAKE A
*ANGE ( POSI;N T[>DS XS FRONT OR BACK2 B
"R & LEFT1 SUP]IOR & 9F]IOR >E S
4T+UI%$4 ,ACLY1 ALL ANIMALS : PROGRESS
0! USE ( 4T9CT MEMB]S H ^! MEMB]S
4T+UI%$ N 0! DI6];ES ( 2F & 2H1 B ONLY (
! REMA9+ TWO PAIRS2 ! PRIOR DI6];E
DIVID+ ^! MEMB]S 96"R & LEFT 7A DI6];E :
M/ APPE> Z SOON Z Y H DIVI.N 96TWO71 &!
O!R DI6];E APPE>+ ( NECESS;Y ": "! IS
DIVI.N 96F\R4
  ,S9CE !N ^! TWO PAIRS1 ! SUP]IOR &
9F]IOR &! "R & LEFT1 >E L9K$ 6"O ANO!R
0! SAME -MON ORIG9AL 70: ,I M1N T :
3TROLS _! MOVE;T71 & FUR!R1 "EY?+ : IS
9T5D$ 6MAKE A MOVE;T 9 EA* S* "P PROP]LY
M/ H ! ORIG9AL CAUSE ( ALL ! SD MOVE;TS
>RANG$ 9 A C]TA9 DEF9ITE POSI;N
RELATIVELY 6! 4T.ES F X (! ORIG9ALS (!
MOVE;TS (! 9DIVIDUAL MEMB]S 7& ^! C5TRES
(! 9DIVIDUAL "PS >E 9 PAIRS >RANG$
COORD9ATELY OR DIAGON,Y1 &! -MON C5TRE
IS ! ORIG9AL F : ! ANIMAL'S MOVE;TS ( "R
& LEFT1 & SIMIL>LY ( SUP]IOR & 9F]IOR1
/>T72 EA* ANIMAL M/ H ? ORIG9AL AT A
PO9T ": X IS EQU,Y OR NE>LY EQU,Y RELAT$
6EA* (! C5TRES 9 ! F\R "PS DESCRIB$4
                   #G
  ,X IS CLE> !N H[ LOCOMO;N 2L;GS 6^?
ANIMALS ONLY : MAKE _! *ANGES ( PLACE
0M1NS ( TWO OR F\R PO9TS 9 _! /RUCTURE1
OR 6S* ANIMALS P> EXCELL;E4 ,MOREOV]1
S9CE ? PROP]TY 2L;GS ALM PECULI>LY
6,SANGU9E\S ANIMALS1 WE SEE T NO
,SANGU9E\S ANIMAL C PROGRESS AT M PO9TS
?AN F\R1 & T IF X IS ! NATURE ( ANY?+ S
6PROGRESS AT F\R PO9TS X M/ ( NECESS;Y 2
,SANGU9E\S4
  ,:AT WE OBS]VE 9 ! ANIMAL _W IS 9
AGREE;T )! ABV A3.T4 ,= NO ,SANGU9E\S
ANIMAL IF X 2 DIVID$ 96M "PS C LIVE =
ANY APPRECIA# L5G? ( "T1 NOR C X 5JOY !
P[] ( LOCOMO;N : X POSSESS$ :ILE X 0 A
3T9U\S & UNDIVID$ :OLE4 ,B "S BLOOD.S
ANIMALS & POLYPODS C LIVE A L;G "T1 IF
DIVID$1 9 EA* (! S"E$ "PS1 & C MOVE 9 !
SAME WAY Z 2F !Y 7 4MEMB]$4 ,EXAMPLES >E
:AT IS T]M$ ! C5TIP$E & O!R 9SECTS T >E
L;G 9 %APE1 = EV5 ! H9D] POR;N ( ALL ^!
GOES ON PROGRESS+ 9 ! SAME DIREC;N Z 2F
:5 !Y >E CUT 9 TWO4
  ,! EXPLAN,N ( _! LIV+ :5 ?US DIVID$ IS
T EA* ( !M IS 3/RUCT$ L A 3T9U\S BODY (
_M SEP>ATE LIV+ 2+S4 ,X IS PLA91 TOO1 F
:AT 0 SD ABV :Y !Y >E L ?4 ,ANIMALS
3/RUCT$ MO/ NATUR,Y >E MADE 6MOVE AT TWO
OR F\R PO9TS1 & EV5 LIMB.S ,SANGU9EA >E
NO EXCEP;N4 ,!Y TOO MOVE 0D9T ( F\R
PO9TS1 ":BY !Y A*IEVE PROGRES.N4 ,!Y G
=W>D 0M1NS ( TWO FLEXIONS4 ,= 9 EA* ( _!
FLEXIONS "! IS A "R &A LEFT1 BO? 2F & 2H
9 _! FLAT SURFACE1 9 ! "P T[>DS ! H1D A
"R &A LEFT FRONT PO9T1 & 9 ! "P T[>DS !
TAIL ! TWO H9D] PO9TS4 ,!Y LOOK Z IF !Y
MOV$ AT TWO PO9TS ONLY1 ": !Y T\* 2F &
2H1 B T IS ONLY 2C !Y >E N>R[ 9 BR1D?4
,EV54 9 !M ! "R IS ! SOV]EIGN "P1 & "!
IS AN ALT]NATE CORRESPOND;E 2H1 EXACTLY
Z 9 QUADRUP$S4 ,! R1SON ( _! FLEXIONS IS
_! GRT L5G?1 = J Z TALL M5 WALK ) _!
SP9ES BELLI$ 7UNDULAT$7 =W>D1 & :5 _! "R
%\LD] IS L1D+ 9 A =W>D DIREC;N _! LEFT
HIP R 9CL9$ BACKW>DS1 S T _! MI4LE
2COMES HOLL[ & BELLI$ 7UNDULAT$71 S WE
"\ 63CV SNAKES Z MOV+ 9 3CAVE CURVES
7UNDUL,NS7 ^U ! GR.D4 ,& ? IS EVID;E T
!Y MOVE !MVS L ! QUADRUP$S1 = !Y MAKE !
3CAVE 9 XS TURN 3VEX &! 3VEX 3CAVE4 ,:5
9 XS TURN ! LEFT (! =W>D "PS IS L1D+1 !
3CAV;Y IS 9 XS TURN REV]S$1 =! "R 2COMES
! 9N]4 7,LET ! "R FRONT PO9T 2 ;,A1 !
LEFT ;,B1 ! "R H9D ;,C1 ! LEFT ,D47
  ,AM;G L& ANIMALS ? IS ! "* (! MOVE;T (
SNAKES1 & AM;G WAT] ANIMALS ( EELS1 &
3G]-EELS & AL LAMPREYS1 9 FACT ( ALL T H
_! =M SNAKELIKE4 ,H["E1 "S M>9E ANIMALS
( ? %APE H NO F91 LAMPREYS = EXAMPLE1 B
PUT ! SEA 6! SAME USE Z SNAKES D BO? L&
& WAT] 7= SNAKES SWIM PRECISELY Z !Y
MOVE ON ! GR.D74 ,O!RS H TWO F9S ONLY1 =
EXAMPLE 3G]-EELS & EELS &A K9D ( CE/REUS
: BRE$S 9 ! LAKE ( ,SIPHAE4 ,ON ? A3.T
TOO ^? T >E A3U/OM$ 6LIVE ON L&1 =
EXAMPLE ALL ! EELS1 MOVE ) FEW] FLEXIONS
9 A FLUID ?AN ON L&1 :ILE ! K9D (
CE/REUS : HAS TWO F9S1 0XS FLEXION 9 A
FLUID MAKES UP ! REMA9+ PO9TS4
                   #H
  ,! R1SON :Y SNAKES >E LIMB.S IS F/ T
NATURE MAKES NO?+ )\T PURPOSE1 B ALW
REG>DS :AT IS ! BE/ POSSI# = EA*
9DIVIDUAL1 PRES]V+ ! PECULI> ESS;E ( EA*
& XS 9T5D$ "*1 & SECONDLY ! PR9CIPLE WE
LAID D[N ABV T NO ,SANGU9E\S CR1TURE C
MOVE XF AT M ?AN F\R PO9TS4 ,GRANT+ ? X
IS EVID5T T ,SANGU9E\S ANIMALS L SNAKES1
^: L5G? IS \ ( PROPOR;N 6! RE/ ( _!
DIM5.NS1 _C POSSIBLY H LIMBS2 = !Y _C H
M ?AN F\R 7OR !Y WD 2 BLOOD.S71 & IF !Y
_H TWO OR F\R !Y WD 2 PRACTIC,Y /,N>Y2 S
SL[ & UNPR(ITA# WD _! MOVE;T NECESS>ILY
BE4
  ,B E LIMB$ ANIMAL HAS NECESS>ILY AN
EV5 NUMB] ( S* LIMBS4 ,= ^? : ONLY JUMP
& S MOVE F PLACE 6PLACE D N NE$ LIMBS =
? MOVE;T AT L1/1 B ^? : N ONLY JUMP B AL
NE$ 6WALK1 F9D+ T MOVE;T N SU6ICI5T = _!
PURPOSES1 EVID5TLY EI >E BETT] A#
6PROGRESS ) EV5 LIMBS OR _C O!RWISE
PROGRESS AT ALL E ANIMAL : HAS LIMBS M/
H AN EV5 U = Z ? K9D ( MOVE;T IS E6ECT$
0"P (! BODY AT A "T1 & N 0! :OLE AT ONCE
Z 9 ! MOVE;T ( L1P+1 "S (! LIMBS M/ 9
TURN REMA9 AT RE/1 & O!RS 2 MOV$1 &!
ANIMAL M/ ACT 9 EA* ( ^! CASES )
OPPOSITE LIMBS1 %IFT+ ! WEI<T F ! LIMBS
T >E 2+ MOV$ 6^? AT RE/4 ,& S NO?+ C
WALK ON ?REE LIMBS OR ON "O2 9 ! LATT]
CASE X HAS NO SUPPORT AT ALL ON : 6RE/ !
BODY'S WEI<T1 9 ! =M] ONLY 9 RESPECT (
"O PAIR ( OPPOSITES1 & S X M/ NECESS>ILY
FALL 9 5D1V\R+ S 6MOVE4
  ,POLYPODS H["E1 L ! ,C5TIP$E1 C 9DE$
MAKE PROGRESS ON AN ODD NUMB] ( LIMBS1 Z
MAY 2 SE5 0! EXP]I;T ( W.D+ "O ( _!
LIMBS2 = !N ! MUTIL,N ( "O R[ ( LIMBS IS
CORRECT$ 0! NUMB] ( LIMBS : REMA9 ON EI
SIDE4 ,S* MUTILAT$ CR1TURES1 H["E1 DRAG
! W.D$ LIMB AF !M )! REMA9D]1 & D N
PROP]LY SP1K+ WALK4 ,MOREOV]1 X IS PLA9
T !Y1 TOO1 WD MAKE ! *ANGE ( PLACE BETT]
IF !Y _H AN EV5 NUMB]1 9 FACT IF N"O 7
MISS+ & !Y _H ! LIMBS : CORRESPOND 6"O
ANO!R4 ,9 ? WAY !Y CD EQUALIZE _! [N
WEI<T1 & N OSCILLATE 6"O SIDE1 IF !Y _H
CORRESPOND+ SUPPORTS 9/1D ( "O SEC;N (!
OPPOSITE SIDES 2+ UNO3UPI$ 0A LIMB4 ,A
WALK+ CR1TURE ADV.ES F EA* ( XS MEMB]S
ALT]NATELY1 = 9 ? WAY X RECOV]S ! SAME
FIGURE T X _H AT F/4
                   #I
  ,! FACT T ALL ANIMALS H AN EV5 NUMB] (
FEET1 &! R1SONS =! FACT H BE5 SET =?4
,:AT FOLL[S W EXPLA9 T IF "! 7 NO PO9T
AT RE/ FLEXION & /RAI<T5+ WD 2 IMPOSSI#4
,FLEXION IS A *ANGE F A "R L9E 6AN >C OR
AN ANGLE1 /RAI<T5+ A *ANGE F EI ( ^! 6A
"R L9E4 ,N[ 9 ALL S* *ANGES ! FLEXION OR
! /RAI<T5+ M/ 2 RELATIVE 6"O PO9T4
,MOREOV]1 )\T FLEXION "! CD N 2 WALK+ OR
SWIMM+ OR FLY+4 ,= S9CE LIMB$ CR1TURES
/& & TAKE _! WEI<T ALT]NATELY ON "O OR
O!R (! OPPOSITE LEGS1 IF "O 2 ?RU/ =W>D
! O!R ( NECESS;Y M/ 2 B5T4 ,=! OPPOSITE
LIMBS >E NATUR,Y ( EQUAL L5G?1 &! "O :
IS "U ! WEI<T M/ 2 A K9D ( P]P5DICUL> AT
"R ANGLES 6! GR.D4
  ,:5 !N "O LEG IS ADV.ED X 2COMES !
HYPOT5USE (A "R-ANGL$ TRIANGLE4 ,XS
SQU>E !N IS EQUAL 6! SQU>E ON ! O!R SIDE
TGR )! SQU>E ON ! BASE4 ,Z ! LEGS !N >E
EQUAL1 ! "O AT RE/ M/ B5D EI AT ! KNEE
OR1 IF "! 7 ANY KNEE.S ANIMAL : WALK$1
AT "S O!R >TICUL,N4 ,! FOLL[+ EXP]I;T
EXHIBITS ! FACT4 ,IF A MAN 7 6WALK
P>ALLEL 6A WALL 9 SUN%9E1 ! L9E DESCRIB$
70! %AD[ ( 8 H1D@> WD 2 N /RAI<T B
ZIGZAG1 2COM+ L[] Z HE B5DS1 & HI<] :5
HE /&S & LIFTS HMF UP4
  ,X IS1 9DE$1 POSSI# 6MOVE "OF EV5 IF !
LEG 2 N B5T1 9 ! WAY 9 : *N CRAWL4 ,? 0
! OLD ?\< ]RONE\S A3.T (! MOVE;T (
ELEPHANTS4 ,B ^! K9DS ( MOVE;TS 9VOLVE A
FLEXION 9 ! %\LD]S OR 9 ! HIPS4 ,NO?+ AT
ANY RATE CD WALK UP"R 3T9U\SLY &
SECURELY )\T FLEXIONS AT ! KNEE1 B WD H
6MOVE L M5 9 ! WRE/L+ S*OOLS :O CRAWL
=W>D "? ! S& ON _! KNEES4 ,=! UPP] "P (!
UP"R CR1TURE IS L;G S T XS LEG HAS 6BE
CORRESPOND+LY L;G2 9 3SEQU;E "! M/ 2
FLEXION4 ,= S9CE A /,N>Y POSI;N IS
P]P5DICUL>1 IF T : MOVES _C B5D X W EI
FALL =W>D Z ! "R ANGLE 2COMES ACUTE OR W
N 2 A# 6PROGRESS4 ,= IF "O LEG IS AT "R
ANGLES 6! GR.D &! O!R IS ADV.ED1 ! LATT]
W 2 AT ONCE EQUAL & GRT]4 ,= X W 2 EQUAL
6! /,N>Y LEG & AL EQUIVAL5T 6! HYPOT5USE
(A "R-ANGL$ TRIANGLE4 ,T : GOES =W>D
"!=E M/ B5D1 & :ILE B5D+ "O1 EXT5D ! O!R
LEG SIMULTANE\SLY1 S Z 69CL9E =W>D &
MAKE A /RIDE & / REMA9 ABV ! P]P5DICUL>2
=! LEGS =M AN ISOSCELES TRIANGLE1 &! H1D
S9KS L[] :5 X IS P]P5DICUL>LY ABV ! BASE
ON : X /&S4
  ,( LIMB.S ANIMALS1 "S PROGRESS
0UNDUL,NS 7& ? HAPP5S 9 TWO WAYS1 EI !Y
UNDULATE ON ! GR.D1 L SNAKES1 OR UP &
D[N1 L CAT]PILL>S71 & UNDUL,N IS A
FLEXION2 O!RS 0A TELESCOPIC AC;N1 L :AT
>E CALL$ E>?WORMS & LEE*ES4 ,^! G =W>D1
F/ "O "P L1D+ & !N DRAW+ ! :OLE (! RE/ (
! BODY UP 6?1 & S !Y *ANGE F PLACE
6PLACE4 ,X IS PLA9 TOO T IF ! TWO CURVES
7 N GRT] ?AN ! "O L9E : SUBT5DS !M
UNDULAT+ ANIMALS CD N MOVE !MVS2 :5 !
FLEXURE IS EXT5D$ !Y WD N H MOV$ =W>D AT
ALL IF ! FLEXURE OR >C 7 EQUAL 6! *ORD
SUBT5D$2 Z X IS1 X R1*ES FUR!R :5 X IS
/RAI<T5$ \1 & !N ? "P /AYS / & X DRAWS
UP :AT IS LEFT 2H4
  ,9 ALL ! *ANGES DESCRIB$ T : MOVES N[
EXT5DS XF 9 A /RAI<T L9E 6PROGRESS1 & N[
IS HOOP$2 X /RAI<T5S XF 9 XS L1D+ "P1 &
IS HOOP$ 9 :AT FOLL[S 2H4 ,EV5 JUMP+
ANIMALS ALL MAKE A FLEXION 9 ! "P (!
BODY : IS "UN1?1 & AF ? FA%ION MAKE _!
L1PS4 ,S TOO FLY+ & SWIMM+ ?+S PROGRESS1
! "O /RAI<T5+ & B5D+ _! W+S 6FLY1 ! O!R
_! F9S 6SWIM4 ,(! LATT] "S H F\R F9S1
O!RS : >E R L;G1 = EXAMPLE EELS1 H ONLY
TWO4 ,^! SWIM 0SUB/ITUT+ A FLEXION (!
RE/ ( _! BODY =! 7MISS+7 PAIR ( F9S
6-PLETE ! MOVE;T1 Z WE H SD 2F4 ,FLAT
FI% USE TWO F9S1 &! FLAT ( _! BODY Z A
SUB/ITUTE =! ABS5T PAIR ( F9S4 ,Q FLAT
FI%1 L ! ,RAY1 PRODUCE _! SWIMM+ MOVE;T
)! ACTUAL F9S &)! TWO EXTREMES OR
SEMICIRCLES ( _! BODY1 B5D+ & /RAI<T5+
!MVS ALT]NATELY4

                  #AJ
  ,A DI6ICULTY MI<T P]H 2 RAIS$ AB
BIRDS4 ,H[1 X MAY 2 SD1 C !Y1 EI :5 !Y
FLY OR :5 !Y WALK1 2 SD 6MOVE AT F\R
PO9TS8 ,N[ WE DID N SAY T ALL ,SANGU9EA
MOVE AT F\R PO9TS1 B M]ELY AT N M ?AN
F\R4 ,MOREOV]1 !Y _C Z A FACT FLY IF _!
LEGS 2 REMOV$1 NOR WALK )\T _! W+S4 ,EV5
A MAN DOES N WALK )\T MOV+ 8 %\LD]S4
,"EY?+ 9DE$1 Z WE H SD1 MAKES A *ANGE (
PLACE 0FLEXION & /RAI<T5+1 = ALL ?+S
PROGRESS 0PRESS+ ^U :AT 2+ 2N !M UP 6A
PO9T GIVES WAY Z X 7 GRADU,Y2 ACLY1 EV5
IF "! 2 NO FLEXION 9 ANO!R MEMB]1 "! M/
2 AT L1/ 9 ! PO9T :;E MO;N 2G9S1 IS 9
F1!R$ 7FLY+7 9SECTS AT ! BASE (!
,8SCALE-W+0'1 9 BIRDS AT ! BASE (! W+1 9
O!RS AT ! BASE (! CORRESPOND+ MEMB]1 !
F9S1 = 9/.E1 9 FI%4 ,9 O!RS1 = EXAMPLE
SNAKES1 ! FLEXION 2G9S 9 ! JO9TS (!
BODY4
  ,9 W+$ CR1TURES ! TAIL S]VES1 L A
%IP'S RU4]1 6KEEP ! FLY+ ?+ 9 XS C\RSE4
,! TAIL !N M/ L O!R LIMBS 2 A# 6B5D AT !
PO9T ( ATTA*;T4 ,& S FLY+ 9SECTS1 &
BIRDS 7,S*IZOPT]A7 ^: TAILS >E ILL-
ADAPT$ =! USE 9 "Q1 = EXAMPLE P1COCKS1 &
DOME/IC COCKS1 & G5],Y BIRDS T H>DLY
FLY1 _C /E] A /RAI<T C\RSE4 ,FLY+ 9SECTS
H ABSOLUTELY NO TAIL1 & S DRIFT AL;G L A
RU4].S VESSEL1 & B1T AG/ ANY?+ !Y HAPP5
^U2 & ? APPLIES EQU,Y 6%>D$ 9SECTS1 L !
SC>AB-BEETLE &! *AF]1 & 6UN%>D$1 L BEES
& WASPS4 ,FUR!R1 BIRDS T >E N MADE =
FLI<T H A TAIL T IS ( NO USE2 = 9/.E !
PURPLE COOT &! H]ON & ALL WAT]-F[L4 ,^!
FLY /RET*+ \ _! FEET Z A SUB/ITUTE =A
TAIL1 & USE _! LEGS 9/1D (A TAIL 6DIRECT
_! FLI<T4 ,! FLI<T ( 9SECTS IS SL[ &
FRAIL 2C ! "* ( _! F1!RY W+S IS N
PROPOR;NATE 6! BULK ( _! BODY2 ? IS
H1VY1 _! W+S SMALL & FRAIL1 & S ! FLI<T
!Y USE IS L A C>GO BOAT ATTEMPT+ 6MAKE
XS VOYAGE ) O>S2 N[ ! FRAILTY BO? (!
ACTUAL W+S &(! \TGR[?S ^U !M 3TRIBUTES 9
A M1SURE 6! FLI<T DESCRIB$4 ,AM;G BIRDS1
! P1COCK'S TAIL IS AT "O "T USE.S 2C (
XS SIZE1 AT ANO!R 2C X IS %$4 ,B BIRDS
>E 9 G5]AL AT ! OPPOSITE POLE 6FLY+
9SECTS Z REG>DS _! F1!RS1 B ESPECI,Y !
SWIFTE/ FLY]S AM;G !M4 7,^! >E ! BIRDS )
CURV$ TALONS1 = SWIFT;S ( W+ IS USE;L
6_! MODE ( LIFE47 ,! RE/ ( _! BODILY
/RUCTURE IS 9 H>MONY ) _! PECULI>
MOVE;T1 ! SMALL H1D1 ! SLI<T NECK1 !
/R;G & ACUTE BR1/B"O 7ACUTE L ! PR[ (A
CLIPP]-BUILT VESSEL1 S Z 6BE WELL-GIRT1
& /R;G 0D9T ( XS MASS ( FLE%71 9 ORD]
6BE A# 6PU% AWAY ! AIR T B1TS AG/ X1 & T
EASILY & )\T EXHAUS;N4 ,! H9D-QU>T]S1
TOO1 >E LI<T & TAP] AG1 9 ORD] 63=M 6!
MOVE;T (! FRONT & N 0_! BR1D? 6SUCK !
AIR4
                  #AA
  ,S M* !N = ^! "QS4 ,B :Y AN ANIMAL T
IS 6/& ERECT M/ NECESS>ILY 2 N ONLY A
BIP$1 B M/ AL H ! SUP]IOR "PS (! BODY
LI<T]1 & ^? T LIE "U ^! H1VI]1 IS PLA94
,ONLY IF SITUAT$ L ? CD X POSSIBLY C>RY
XF EASILY4 ,& S MAN1 ! ONLY ERECT
ANIMAL1 HAS LEGS L;G] & /\T] RELATIVELY
6! UPP] "PS ( 8 BODY ?AN ANY O!R ANIMAL
) LEGS4 ,:AT WE OBS]VE 9 *N AL IS EVID;E
( ?4 ,*N _C WALK ERECT 2C !Y >E ALW
DW>F-L1 ! UPP] "PS ( _! BODIES 2+ L;G] &
/\T] ?AN ! L[]4 ,) ADVANC+ YE>S ! L[]
9CR1SE 4PROPOR;NATELY1 UNTIL ! *N GET _!
APPROPRIATE SIZE1 & !N & N TILL !N !Y
SU3E$ 9 WALK+ ERECT4 ,BIRDS >E HUN*BACK$
YET /& ON TWO LEGS 2C _! WEI<T IS SET
BACK1 AF ! PR9CIPLE ( HORSES FA%ION$ 9
BRONZE ) _! =ELEGS PRANC+4 ,B _! 2+
BIP$S & A# 6/& IS ABV ALL DUE 6_! HAV+ !
HIP-B"O %AP$ L A ?I<1 & S L>GE T X LOOKS
Z IF !Y _H TWO ?I<S1 "O 9 ! LEG 2F !
KNEE-JO9T1 ! O!R JO9+ 8 "P 6! FUNDA;T4
,RE,Y ? IS N A ?I< B A HIP1 & IF X 7 N S
L>GE ! BIRD CD N 2 A BIP$4 ,Z 9 A MAN OR
A QUADRUP$1 ! ?I< &! RE/ (! LEG WD 2
ATTA*$ IMMLY 6Q A SMALL HIP2 3SEQU5TLY !
:OLE BODY WD 2 TILT$ =W>D4 ,Z X IS1
H["E1 ! HIP IS L;G & EXT5DS "R AL;G 6!
MI4LE (! BELLY1 S T ! LEGS >E ATTA*$ AT
T PO9T & C>RY Z SUPPORTS ! :OLE FRAME4
,X IS AL EVID5T F ^! 3SID],NS T A BIRD
_C POSSIBLY 2 ERECT 9 ! S5SE 9 : MAN IS4
,= Z X HOLDS XS BODY N[ ! W+S >E NATUR,Y
USE;L 6X1 B IF X 7 ERECT !Y WD 2 Z USE.S
Z ! W+S ( ,CUPIDS WE SEE 9 PICTURES4 ,X
M/ H BE5 CLE> Z SOON Z WE SPOKE T ! =M (
NO HUMAN NOR ANY SIMIL> 2+ P]MITS ( W+S2
N ONLY 2C X WD1 ?\< ,SANGU9E\S1 2 MOV$
AT M ?AN F\R PO9TS1 B AL 2C 6H W+S WD 2
USE.S 6X :5 MOV+ NATUR,Y4 ,& ,NATURE
MAKES NO?+ 3TR>Y 6H] [N NATURE4
                  #AB
  ,WE H /AT$ ABV T )\T FLEXION 9 ! LEGS
OR %\LD]S & HIPS NO ,SANGU9E\S ANIMAL )
FEET CD PROGRESS1 & T FLEXION IS
IMPOSSI# EXCEPT "S PO9T 2 AT RE/1 & T M5
& BIRDS1 BO? BIP$S1 B5D _! LEGS 9
OPPOSITE DIREC;NS1 & FUR!R T QUADRUP$S
B5D _! 9 OPPOSITE DIREC;NS1 & EA* PAIR 9
! OPPOSITE WAY 6A MAN'S LIMBS4 ,= M5 B5D
_! >MS BACKW>DS1 _! LEGS =W>DS2
QUADRUP$S _! =ELEGS =W>DS1 _! BACK LEGS
BACKW>DS1 & 9 L MANN] AL BIRDS B5D _!S4
,! R1SON IS T ,NATURE'S "WMAN%IP IS N"E
PURPOSE.S1 Z WE SD ABV1 B "EY?+ =! BE/
POSSI# 9 ! CIRCUM/.ES4 ,9ASM*1 "!=E1 Z
ALL CR1TURES : NATUR,Y H ! P[] ( *ANG+
POSI;N 0! USE ( LIMBS1 M/ H "O LEG /,N>Y
)! WEI<T (! BODY ON X1 & :5 !Y MOVE =W>D
! LEG : HAS ! L1D+ POSI;N M/ 2
UN5CUMB]$1 &! PROGRES.N 3T9U+ ! WEI<T M/
%IFT & 2 TAK5 (F ON ? L1D+ LEG1 X IS
EVID5TLY NEC =! BACK LEG F 2+ B5T 62COME
/RAI<T AG1 :ILE ! PO9T ( MOVE;T (! LEG
?RU/ =W>D & XS L[] "P REMA9 /4 ,& S !
LEGS M/ 2 JO9T$4 ,& X IS POSSI# = ?
6TAKE PLACE & AT ! SAME "T =! ANIMAL 6G
=W>D1 IF ! L1D+ LEG HAS XS >TICUL,N
=W>DS1 IMPOSSI# IF X 2 BACKW>DS4 ,=1 IF
X 2 =W>DS1 ! /RET*+ \ (! LEG W 2 :ILE !
BODY IS GO+ =W>DS1 B1 IF ! O!R WAY1 :ILE
X IS GO+ BACKW>DS4 ,& AG1 IF ! FLEXION 7
BACKW>DS1 ! PLAC+ (! FOOT WD 2 MADE 0TWO
MOVE;TS & ^? 3TR>Y 6"O ANO!R1 "O1 T IS1
BACKW>DS & "O =W>DS2 = 9 ! B5D+ TGR (!
LIMB ! L[] 5D (! ?I< WD G BACKW>DS1 &!
%9 WD MOVE ! FOOT =W>DS AWAY F !
FLEXION2 ":AS1 )! FLEXION =W>DS1 !
PROGRES.N DESCRIB$ W 2 P]=M$ N ) 3TR>Y
MO;NS1 B ) "O =W>D MO;N4
  ,N[ MAN1 2+ A BIP$ & MAK+ 8 *ANGE (
POSI;N 9 ! NATURAL WAY ) 8 TWO LEGS1
B5DS !M =W>D =! R1SONS SET =?1 B 8 >MS
B5D BACKW>DS R1SONABLY 5\<4 ,IF !Y B5T !
OPPOSITE WAY !Y WD 2 USE.S =! "W (! H&S1
&= TAK+ FOOD4 ,B QUADRUP$S : >E AL
VIVIP>\S NECESS>ILY B5D _! FRONT LEGS
=W>DS4 ,= ^! L1D (F F/ :5 !Y MOVE1 & >E
AL 9 ! =E"P ( _! BODY4 ,! R1SON T !Y B5D
=W>D IS ! SAME Z 9 ! CASE ( MAN1 = 9 ?
RESPECT !Y >E L MANK9D4 ,& S QUADRUP$S Z
WELL Z M5 B5D ^! LEGS =W>D 9 ! MANN]
DESCRIB$4 ,MOREOV]1 IF ! FLEXION IS L ?1
!Y >E 5A#D 6LIFT _! FEET HI<2 IF !Y B5T
!M 9 ! OPPOSITE WAY !Y WD ONLY LIFT !M A
LL WAY F ! GR.D1 2C ! :OLE ?I< &! JO9T F
: ! %9-B"O SPR+S WD LIE "U ! BELLY Z !
B1/ MOV$ =W>D4 ,IF1 H["E1 ! FLEXION (!
H9D LEGS 7 =W>DS ! LIFT+ ( ^! FEET WD 2
SIMIL> 6T (! =EFEET 7=! H9D LEGS1 TOO1
WD 9 ? CASE H ONLY A LL ROOM = _! LIFT+
9ASM* Z BO? ! ?I< &! KNEE-JO9T WD FALL
"U ! POSI;N (! BELLY72 B ! FLEXION 2+
BACKW>DS1 Z 9 FACT X IS1 NO?+ -ES 9 !
WAY ( _! PROGRES.N ) ? MODE ( MOV+ !
FEET4 ,MOREOV]1 X IS NEC OR AT L1/ BETT]
= _! LEGS 6B5D ?US :5 !Y >E SUCKL+ _!
"Y1 )A VIEW 6S* M9I/R,NS4 ,IF ! FLEXION
7 9W>DS X WD 2 DI6ICULT 6KEEP _! "Y "U
!M & 6%ELT] !M4
                  #AC
  ,N[ "! >E F\R MODES ( FLEXION IF WE
TAKE ! -B9,NS 9 PAIRS4 ,=E & H9D MAY B5D
EI BO? BACKW>DS1 Z ! FIGURES M>K$ ;,A1
OR 9 ! OPPOSITE WAY BO? =W>DS1 Z 9 ;,B1
OR 9 3V]SE WAYS & N 9 ! SAME DIREC;N1 Z
9 ;,C ": ! =E B5D =W>DS &! H9D B5D
BACKW>DS1 OR Z 9 ;,D1 ! OPPOSITE WAY TO
;,C1 ": ! 3VEXITIES >E TURN$ T[>DS "O
ANO!R &! 3CAVITIES \TW>DS4 ,N[ NO BIP$
OR QUADRUP$ B5DS 8 LIMBS L ! FIGURES ,A
OR ;,B1 B ! QUADRUP$S L ;,C1 & L ;,D
ONLY ! ELEPHANT AM;G QUADRUP$S & MAN IF
Y 3SID] 8 >MS Z WELL Z 8 LEGS4 ,= HE
B5DS 8 >MS 3CAVELY & 8 LEGS 3VEXLY4
  ,9 MAN1 TOO1 ! FLEXIONS (! LIMBS >E
ALW ALT]NATELY OPPOSITE1 = EXAMPLE !
ELB[ B5DS BACK1 B ! WRI/ (! H& =W>DS1 &
AG ! %\LD] =W>DS4 ,9 L FA%ION1 TOO1 9 !
CASE (! LEGS1 ! HIP BACKW>DS1 ! KNEE
=W>DS1 ! ANKLE 9 ! OPPOSITE WAY
BACKW>DS4 ,& PLA9LY ! L[] LIMBS >E
OPPOS$ 9 ? RESPECT 6! UPP]1 2C ! F/
JO9TS >E OPPOSITES1 ! %\LD] B5D+ =W>DS1
! HIP BACKW>DS2 ":=E AL ! ANKLE B5DS
BACKW>DS1 &! WRI/ (! H& =W>DS4
                  #AD
  ,? IS ! WAY !N ! LIMBS B5D1 &=! R1SONS
GIV54 ,B ! H9D LIMBS MOVE CRISS-CROSS )!
=E LIMBS2 AF ! (F =E !Y MOVE ! NE> H9D1
!N ! NE> =E1 & !N ! (F H9D4 ,! R1SON IS
T 7A7 IF !Y MOV$ ! =ELEGS TGR & F/1 !
ANIMAL WD 2 WR5*$1 &! PROGRES.N WD 2 A
/UMBL+ =W>DS )! H9D "PS Z X 7 DRA7$ AF4
,AG1 T WD N 2 WALK+ B JUMP+1 & X IS H>D
6MAKE A 3T9U\S *ANGE ( PLACE1 JUMP+ ALL
! "T4 ,"H IS EVID;E ( :AT ,I SAY2 EV5 Z
X IS1 ALL HORSES T MOVE 9 ? WAY SOON 2G9
6REFUSE1 = EXAMPLE ! HORSES 9 A RELIGI\S
PROCES.N4 ,= ^! R1SONS ! =E LIMBS &! H9D
LIMBS MOVE 9 ? SEP>ATE WAY4 ,AG1 7B7 IF
!Y MOV$ BO? ! "R LEGS F/ ! WEI<T WD 2
\TSIDE ! SUPPORT+ LIMBS & !Y WD FALL4
,IF !N X IS NEC 6MOVE 9 "O OR O!R ( ^!
WAYS OR CRISS-CROSS FA%ION1 & NEI ( ^!
TWO IS SATISFACTORY1 !Y M/ MOVE CRISS-
CROSS2 = MOV+ 9 ! WAY WE H SD !Y _C
POSSIBLY EXP]I;E EI ( ^! UNT[>D RESULTS4
,& ? IS :Y HORSES & S*-L ANIMALS /& / )
_! LEGS PUT =W>D CRISS-CROSS1 N )! "R OR
! LEFT PUT =W>D TGR AT ONCE4 ,9 ! SAME
FA%ION ANIMALS ) M ?AN F\R LEGS MAKE _!
MOVE;TS2 IF Y TAKE TWO 3SECUTIVE PAIRS (
LEGS ! H9D MOVE CRISS-CROSS )! =ELEGS2 Y
C SEE ? IF Y WAT* !M MOV+ SL[LY4 ,EV5
CRABS MOVE 9 ? WAY1 & !Y >E POLYPODS4
,!Y1 TOO1 ALW MOVE CRISS-CROSS 9 :I*"E
DIREC;N !Y >E MAK+ PROGRESS4 ,= 9
DIREC;N ? ANIMAL HAS A MOVE;T ALL XS [N2
X IS ! ONLY ANIMAL T MOVES N =W>DS1 B
OBLIQUELY4 ,YET S9CE =W>DS IS A 4T9C;N
RELATIVE 6! L9E ( VI.N1 ,NATURE HAS MADE
XS EYES A# 63=M 6XS LIMBS1 = XS EYES C
MOVE !MVS OBLIQUELY1 & "!=E AF A FA%ION
CRABS >E NO EXCEP;N B 9 ? S5SE MOVE
=W>DS4

                  #AE
  ,BIRDS B5D _! LEGS 9 ! SAME WAY Z
QUADRUP$S4 ,= _! NATURAL 3/RUC;N IS
BROADLY SP1K+ NE>LY ! SAME4 ,T IS1 9
BIRDS ! W+S >E A SUB/ITUTE =! =ELEGS2 &
S !Y >E B5T 9 ! SAME WAY Z ! =ELEGS (A
QUADRUP$1 S9CE :5 !Y MOVE 6PROGRESS !
NATURAL 2G9N+ ( *ANGE IS F ! W+S 7Z 9
QUADRUP$S F ! =ELEGS74 ,FLI<T 9 FACT IS
_! APPROPRIATE MOVE;T4 ,& S IF ! W+S 2
CUT (F A BIRD C NEI /& / NOR G =W>DS4
  ,AG1 ! BIRD ?\< A BIP$ IS N ERECT1 &
HAS ! =W>D "PS (! BODY LI<T] ?AN ! H9D1
& S X IS NEC 7OR AT L1/ PREF]A# =! /&+
PO/URE7 6H ! ?I< S PLAC$ 2L ! BODY Z X
ACTU,Y IS1 ,I M1N GR[+ T[>DS ! BACK4 ,IF
!N X M/ H ? SITU,N ! FLEXION (! LEG M/ 2
BACKW>DS1 Z 9 ! H9D LEGS ( QUADRUP$S4 ,!
R1SONS >E ! SAME Z ^? GIV5 9 ! CASE (
VIVIP>\S QUADRUP$S4
  ,IF N[ WE SURVEY G5],Y BIRDS & W+$
9SECTS1 & ANIMALS : SWIM 9 A WAT]Y
M$IUM1 ALL ,I M1N T MAKE _! PROGRESS 9
WAT] 0D9T ( ORGANS ( MOVE;T1 X IS N
DI6ICULT 6SEE T X IS BETT] 6H ! ATTA*;T
(! "PS 9 "Q OBLIQUE 6! FRAME1 EXACTLY Z
9 FACT WE SEE X 6BE BO? 9 BIRDS &
9SECTS4 ,& ? SAME >RANGE;T OBTA9S AL
AM;G FI%ES4 ,AM;G BIRDS ! W+S >E ATTA*$
OBLIQUELY2 S >E ! F9S 9 WAT] ANIMALS1 &!
F1!R-L W+S ( 9SECTS4 ,9 ? WAY !Y DIVIDE
! AIR OR WAT] MO/ QKLY &) MO/ =CE & S
E6ECT _! MOVE;T4 ,=! H9D] "PS 9 ? WAY WD
FOLL[ =W>DS Z !Y >E C>RI$ AL;G 9 !
YIELD+ M$IUM1 FI% 9 ! WAT]1 BIRDS 9 !
AIR4
  ,( OVIP>\S QUADRUP$S ALL ^? T LIVE 9
HOLES1 L CROCODILES1 LIZ>DS1 SPOTT$
LIZ>DS1 FRE%WAT] TORTOISES1 & TURTLES1 H
_! LEGS ATTA*$ OBLIQUELY Z _! :OLE BODY
SPRAWLS OV] ! GR.D1 & B5D !M OBLIQUELY4
,! R1SON IS T ? IS USE;L = EASE 9 CREEP+
96HOLES1 &= SITT+ ^U _! E7S & GU>D+ !M4
,& Z !Y >E SPLAY$ \TW>DS !Y M/ (
NECESS;Y TUCK 9 _! ?I<S & PUT !M "U !M 9
ORD] 6A*IEVE ! LIFT+ (! :OLE BODY4 ,9
VIEW ( ? !Y _C B5D !M O!RWISE ?AN
\TW>DS4

                  #AF
  ,WE H ALR /AT$ ! FACT T NON-SANGU9E\S
ANIMALS ) LIMBS >E POLYPODS & N"O ( !M
QUADRUP$S4 ,&! R1SON :Y _! LEGS1 EXCEPT
! EXTREME PAIRS1 7 NECESS>ILY ATTA*$
OBLIQUELY & _H _! FLEXIONS UPW>DS1 &!
LEGS !MVS 7 "S:AT TURN$ "U 7B&Y-%APE7 &
BACKW>DS IS PLA94 ,9 ALL S* CR1TURES !
9T]M$IATE LEGS BO? L1D & FOLL[4 ,IF !N
!Y LAY "U !M1 !Y M/ H _H _! FLEXION BO?
=W>DS & BACKW>DS2 ON A3.T ( L1D+1 =W>DS2
& ON A3.T ( FOLL[+1 BACKW>DS4 ,N[ S9CE
!Y H 6D BO?1 = ? R1SON _! LIMBS >E TURN$
"U & B5T OBLIQUELY1 EXCEPT ! TWO EXTREME
PAIRS4 7,^! TWO >E M NATURAL 9 _!
MOVE;T1 ! FRONT L1D+ &! BACK FOLL[+47
,ANO!R R1SON = ? K9D ( FLEXION IS !
NUMB] ( _! LEGS2 >RANG$ 9 ? WAY !Y WD
9T]F]E LESS ) "O ANO!R 9 PROGRES.N & N
KNOCK TGR4 ,B ! R1SON T !Y >E B&Y IS T
ALL ( !M OR MO/ ( !M LIVE 9 HOLES1 =
CR1TURES LIV+ S _C POSSIBLY 2 HI< ABV !
GR.D4
  ,B CRABS >E 9 NATURE ! O4E/ ( ALL
POLYPODS2 !Y D N PROGRESS =W>DS EXCEPT 9
! S5SE EXPLA9$ ABV1 !Y >E ! ONLY ANIMALS
: H M ?AN "O PAIR ( L1D+ LIMBS4 ,!
EXPLAN,N ( ? IS ! H>D;S ( _! LIMBS1 &!
FACT T !Y USE !M N = SWIMM+ B = WALK+2
!Y ALW KEEP ON ! GR.D4 ,H["E1 ! FLEXION
(! LIMBS ( ALL POLYPODS IS OBLIQUE1 L T
(! QUADRUP$S : LIVE 9 HOLES-= EXAMPLE
LIZ>DS & CROCODILES & MO/ (! OVIP>\S
QUADRUP$S4 ,&! EXPLAN,N IS T "S ( !M 9
_! BRE$+ P]IODS1 & "S ALL _! LIFE1 LIVE
9 HOLES4
                  #AG
  ,N[ ! RE/ H B&Y LEGS 2C !Y >E S(T-
SK9N$1 B ! CRAYFI% IS H>D-SK9N$ & XS
LIMBS >E = SWIMM+ & N = WALK+ 7& S >E N
B&Y74 ,CRABS1 TOO1 H _! LIMBS B5T
OBLIQUELY1 B N B&Y L OVIP>\S QUADRUP$S &
NON-SANGU9E\S POLYPODS1 2C _! LIMBS H A
H>D & %ELL-L SK91 AL? !Y DON'T SWIM B
LIVE 9 HOLES2 !Y LIVE 9 FACT ON ! GR.D4
,MOREOV]1 _! %APE IS L A DISK1 Z -P>$ )!
CRAYFI% : IS EL;GAT$1 & !Y HAV5'T A TAIL
L ! CRAYFI%2 A TAIL IS USE;L 6! CRAYFI%
= SWIMM+1 B ! CRAB IS N A SWIMM+
CR1TURE4 ,FUR!R1 X AL"O HAS XS SIDE
EQUIVAL5T 6A H9D] "P1 2C X HAS _M L1D+
FEET4 ,! EXPLAN,N ( ? IS T XS FLEXIONS
>E N =W>D NOR XS LEGS TURN$ 9 "U 7B&Y74
,WE H GIV5 ABV ! R1SON :Y XS LEGS >E N
TURN$ 9 "U1 T IS ! H>D;S & %ELL-L "* (
XS 9TEGU;T4
  ,= ^! R1SONS !N X M/ L1D (F ) M ?AN "O
LIMB1 & MOVE OBLIQUELY2 OBLIQUELY1 2C !
FLEXION IS OBLIQUE2 &) M ?AN "O LIMB1 2C
O!RWISE ! LIMBS T 7 / WD H GOT 9 ! WAY (
^? T 7 MOV+4
  ,FI%ES (! FLAT K9D SWIM ) _! H1DS
TWI/$1 Z "O-EY$ M5 WALK2 !Y H _! NATURAL
%APE 4TORT$4 ,WEB-FOOT$ BIRDS SWIM ) _!
FEET2 2C !Y BR1? ! AIR & H LUNGS !Y >E
BIP$S1 B 2C !Y H _! HOME 9 ! WAT] !Y >E
WE2$2 0? >RANGE;T _! FEET S]VE !M 9/1D (
F9S4 ,!Y H _! LEGS TOO1 N L ! RE/ (
BIRDS 9 ! C5TRE ( _! BODY1 B R SET BACK4
,_! LEGS >E %ORT1 & 2+ SET BACK >E
S]VICEA# = SWIMM+4 ,! R1SON = _! HAV+
%ORT LEGS IS T NATURE HAS A4$ 6_! FEET
0SUBTRACT+ F ! L5G? ( _! LIMBS2 9/1D (
L5G? %E GIVES /\T;S 6! LEGS & BR1D? 6!
FEET4 ,BROAD FEET >E M USE;L ?AN L;G =
PU%+ AWAY ! WAT] :5 !Y >E SWIMM+4
                  #AH
  ,"! IS R1SON1 TOO1 = W+$ CR1TURES HAV+
FEET1 B FI% N"O4 ,! =M] H _! HOME 9 !
DRY M$IUM1 & _C REMA9 ALW 9 MID AIR2 !Y
M/ "!=E H FEET4 ,FI% ON ! 3TR>Y LIVE 9 !
WET M$IUM1 & TAKE 9 WAT]1 N AIR4 ,F9S >E
USE;L = SWIMM+1 B FEET N4 ,& IF !Y _H
BO? !Y WD 2 NON-SANGU9E\S4 ,"! IS A
BROAD SIMIL>;Y 2T BIRDS & FI%ES 9 !
ORGANS ( LOCOMO;N4 ,BIRDS H _! W+S ON !
SUP]IOR "P1 SIMIL>LY FI% H TWO PECTORAL
F9S2 AG1 BIRDS H LEGS ON _! "U "PS & NE>
! W+S2 SIMIL>LY1 MO/ FI% H TWO F9S ON !
"U "PS & NE> ! PECTORALS4 ,BIRDS1 TOO1 H
A TAIL & FI% A TAIL-F94

                  #AI
  ,A DI6ICULTY MAY 2 SU7E/$ Z 6! MOVE;TS
( MOLLUSCS1 T IS1 Z 6": T MOVE;T
ORIG9ATES2 = !Y H NO 4T9C;N ( LEFT & "R4
,N[ OBS]V,N %[S !M MOV+4 ,WE M/1 ,I ?9K1
TR1T ALL ? CLASS Z MUTILAT$1 & Z MOV+ 9
! WAY 9 : LIMB$ CR1TURES D :5 "O CUTS (F
_! LEGS1 OR Z ANALOG\S )! S1L &! BAT4
,BO? ! LATT] >E QUADRUP$S B MIS%AP54 ,N[
MOLLUSCS D MOVE1 B MOVE 9 A MANN] 3TR>Y
6NATURE4 ,!Y >E N MOV+ ?+S1 B >E MOV+ IF
Z S$5T>Y CR1TURES !Y >E -P>$ )
ZOOPHYTES1 & S$5T>Y IF CLASS$ )
PROGRESS+ ANIMALS4
  ,Z 6"R & LEFT1 CRABS1 TOO1 %[ ! 4T9C;N
POORLY1 / !Y D %[ X4 ,Y C SEE X 9 !
CLAW2 ! "R CLAW IS L>G] & /R;G]1 Z ?\< !
"R & LEFT SIDES 7 TRY+ 6GET 4T+UI%$4
  ,! /RUCTURE ( ANIMALS1 BO? 9 _! O!R
"PS1 & ESPECI,Y 9 ^? : 3C]N PROGRES.N &
ANY MOVE;T 9 PLACE1 IS Z WE H N[
DESCRIB$4 ,X REMA9S1 AF DET]M9+ ^! "QS1
69VE/IGATE ! PRO#MS ( ,LIFE & ,D1?4

