I 



128 



BULLKTIN OF THE I'XITKD STATEH FISH COMMISSION. 



Sin 



raiiiilv III- Hiilifiiiilly. 



Aripi'iiHciiilii' ... 

 ('aloHtiiiiiiiiii*. . . . 



C'\ prill iilii' 



,Siiliiiiiiiiil>r 



(',vpi'iii<Hliiiitiilii' 

 (iiisli riiyiciilii' .. 

 Ci'iitiiiiiliiilir... 

 riilliilii 



I'acilii slippi . 

 lirlirta. SprrifH. 



:! 



5 

 4 



1 

 8 



^Vc Irani rnmi tlu'.sc tublt- nat in all laiiiilies but the Cypiinoilmitidn with iiini 



than on«' spnit'.s on tin- Parific sloite the «'.\t«'iit of variation is un'at<'i' than in li 



wunc faniilii's on the Atlantic .slojir.* This iiiiKht have l»e» .xpocted if the ninii>» 



of spci-ies were ^-reatcidii the Paeilic than on the Atlantic slope, but in most ca^ , .*"" 



the reverse is true, as niav 1m' seen from the following table: .^®" 



variatid 



seuHe lo 



tiie re^rj 



I>henoin 



fiesli-w! 



basin, li 



Atlanth 



iiiereu8e( 



offered b 



Hu8, whil 



For I 



tho Soiif 



i Ithatnditt 



iteeuljar t 



^emarknb 



ho Amaz 



lave 7 do 



It 18 t 



ipecies fo 

 uy preset 

 minute III 

 lore 80 t 

 iff'ereuee.' 

 onceive<l 

 lay attenl 

 The pi 

 -miua, t! 

 ver systj 

 • an elex-il 

 ■ stem, 

 tah. Tl 

 lese speJ 

 'monstral 

 Befonf 



ly to 8t;i[ 



iiera of 

 tl lateral 

 St, varial 

 «; secoi 

 o considl 

 rposes. 



I ciiti conceive of Init three i)ossil»lc ex]ilanatioiis for this variation: 



(1) 'flic I'acilic slojic fauna maybe new as compared with the Atlantic, 

 etanparativcly new conditions may have thrown the characters into a ciHiditim 

 iliistaljlee<|nilibriiini with the selection of the adapted forms. The llnctuations in 

 tin rays of some of tiie species would lend weijiht to such a supposition. 



(2) The I'acilic slope fauna may lie of diverse ori<'in. 



('.S) IJotli of these factors may have contributed to briny alxuit the present eoiidit 



This last seems to me to be the true solution. Most of the Ibrms have uinln: 

 edly been derived within c(»mparatively recent time from he Atlantic slope of >"i 

 America, while others liaxe a decidedly Asiatic cast. 



.lc//> //.sv.'- and Oiir()ili!/iu-lnis are certainly of Asiatic (U'iyin. While 1 am not >i 

 ciently aciiiiainted with Asiatic minnows to speak with certainty, .soiiu! of the <^n 

 of miniows seem to have a decided Asiatic allinity. 



]\Iany of ihe Ctifotitdiiiiiuv, the Ci/priiiiihr, and Salreli)iu,s, ArcliopliUs, and pr<ili;i 

 CottiiN have all been derived from forms from the east«'rn slojie of ^'ortli Anierii a. 



* Till' only iitliiT ('xoi'i)tioii is iiitrodiirt'il liy Tliiimiilliin. 



