•)-> 



SCAN 1 )I N" AVIAN FISHES. 



of tlje bo(l\- wliicli is charat-lcristic of tlir Aiinrican form, ami \\liirli. 

 in spite of the variations that accompany tlie usual cliangcs of growtli , 

 and the difference of eex, cannot be regarded as entirely wanting in : 

 significance. As a rule, in JJn'/'iinojiscttd pliiteKSoidcs. the grealest , 

 depth of tlie body is more, in Prep. lirnandoideK less, than ?ih % of 1 

 tlie lengtli I'f tlie liody ; and in consecjiiencc, the length of Ihe head 

 in the former is less than (i.'j "., in the latter more llian 114 %", the 

 postorbital lenglli of (hi- head in the former less, in tlie latter more, 

 than 37','., "i, and the hngtli of the branch of the lower jaw (.n the 

 eve side in the former less than '28 ''„, in the latter more than :i() % 

 — all in proportion to the greatest depth of the body. The same 

 relation is also expressed by the fact that the least depth of the boily 

 (across the peduncle of the tail) in J>rep. platesfioidef: is more than 

 70 »o, in Drep. limandoides less than 72 "o. of the length of the 

 branch of tlie lower jaw on the eye side. .-\notlier eharaeter which ■ 

 also seems to lie constant in adnlt specimens, lies in the fact that 

 the greatest thickness of llie body in Drep. platessoide.': is more, in 

 f'rrp. liiiicniiloide.' less, than - ., of the length of this branch of the 



hiwer jaw. \\"c have here to consider the same ipiestitin as we have 

 just discussed witli reference to the distinction between Pleuroiiecte.< 

 (/l(ii-i(di.-< and J'l. c/i-atru-o.^iis. It may indeed be true that during 

 youth these forms i.-annot be distinguished — in any ease we have not 

 sufficient knowledge of their early stages to decide, lint (hiring the 

 latter ]iail of their development they are distinctly separated, and, 

 strange to say. the diti'erenee between J>rc-p. pdatessoide.'' and Ih-rp. 

 liiiiiiiidoide.^ runs ]iarallel to that between I'leiir. </hiduli.i and Pleiir. 

 ciciitriro.-'ii.-^, jusi as the latter difference has proved above to be parallel 

 to that between /'leiir. yi/'(^wi( and J'leiir. /[(■.•<ii.'<. In all three eases 

 the differentiation of form has taken the same course. In the Plaice 

 and the Flounder it has indeed advanced further, but not even these 

 species have escaped the sus]iieion of being 'dinks in a common series 

 of forms, made up of the finest sliades of difference." 



The ffillowing- table shows partly the most important changes 

 of growth in 1 >rcpa)iopsettii Jiiiiinidoidi'x as it increases in length from 

 'i2S to 315 mm., and partly the relation of this form (on an average) 

 to /'/Y';i. phite.'iKoide.i while between 310 and SOli mm. in length: 



ftrej'itni'i'stttn /iiniui'lniftt-..--. 



Lenjitli 1)1' ilic iiml}, e\|ire.ssiil in aiilliinctrt' 

 Tiitiil U-ie.;lli of llii' lic:i(l 



Pd.sUiiiiiliil IcliL'lli III llir liciid 



3 specimens 



3 specimens 



(QQ9)- 



.1 S]K'L'l)lieilS 



of Ih'ep. pla- 

 tessoides. 



Ab'iisiirellirllts 



of !i "^" spcei- 



nicn of Ih-eji. 



phite.'isnhlcs 



from Halifax 



ill '. of the Iciiu-lli of tlic l)ocl\ 



Grealesl ilciilli iif tlic liod^ _ 



I.cn^'tli nl Hie liriiiieli nf I lii' Iuvmt jiiw on Ilii- blind side. 



I Disliiiice liclHcin Ilic dorsiil tin and Ilic lip of tlic snout. 



Len<;tli (hiiscl of llii' doi-siil lin - -. 



1 HciKlit (lomiest riivl of llu- dor-;il lin 



I Uistillice liel"ccii Ilic iiniil lin :ind Ilic liji of (lie snniil... 



Lcnirtli (liasc) of (he iiniil (in - 



.Height (louijesl rii_\ ) of Ilic iinal lin 



bcn^lli of Ilic |irct<ir:il tin on (he c\c side 



hlind 



M'lilnil .. .. .. eye ,. 



hiiiid 



.. cniidril .. Ill Ihc middle 



■I'ntiil lenitlh .il (he heud 



I'ostorhidil leii'.:(h ol ihc head 



Least de]i(li of (he body in ". of the Icnirlh oldie lii-aiiih o( Ihe loucrjavv mi (lie eye side 



CrcalesI thiekncss of the bodv 



in % of (lie ..'icalesl dcplli >d' (be body 



■JI-J- 

 21 7 



12.11 



32.1 



7.1 



11. s 



10.3 



O.ii 



70. s 



11.1 



2!i.(i 



52. s 

 il.r, 



lO.s 

 8,1 



7,R 



S.d 



li-.L' 



C.T.i; 



-10. L' 



I ill. 7 

 (il.7 



53.0 

 '.1.1 

 11. 1 



S.4 

 1(5.8 



I lit a 

 4 2. a 



i;(;.7 

 I'lifii 



:U1.7 



21.1 

 12.7 



.'!7.ii 

 s.o 



11.11 



;i.!i 



5.7 



7.3.1 



'.1.4 



2;t.o 



57. :i 



;t.2 



10.7 



s.o 



7.8'' 

 8.5' 



15. 1 



57.1 

 34.0 

 SO.i; 

 70.1 



The table shows distinctly that in hardly a single one of Ihe males; while in others the scries diies indeed run in the same di- 



average relations does llrepatiopnelta ptatt-ssoidcn lit exactly into (he \ rection. rising or falling in all three of the first colnmiis. but is ir- 



series of the changes of growth. In some eases the series is broljen regular, with loo wide or loo narrow a gaji between the second and 



by the average measurement of this form, which in these res]iec(s I third columns, this being due to the fact that the characters ot a 



represents the characters holh of the young speciim ns and the fe- 1 male specimen have been iniluded in the third column of averages. 



" The nnnimum proportion in (his res]ieit in all the s|ieeiniens exaniined by Coi.i.ktt was fi6 %. 



* In its capacity of a change of gTOulh (his nlation is less than would have been the resull of .i uniform course of divelopnient. 



