48 ORIGIN OF THE BLIND FISHES. 



as well developed as those of Chologaster cornutus, an argument 

 in favor of the theory that the fishes were always blind and that 

 they have not become so from the circumstances under which they 

 exist? If the latter were the case and the fishes have become blind 

 from the want of use of the eyes, why are not the optic lobes also 

 atrophied, as is known to be the case when other animals lose their 

 sight ? I know that many will answer at once that Amblyopsis 

 and Typhlichthys have gone on further in the development and 

 retardation of the characters best adapting them to their subterra- 

 nean life, and that Chologaster is a very interesting transitionary. 

 form between the open water Cyprinodontes and the subterranean 

 blind fishes. But is not this assumption answered by the fact that 

 Chologaster has every character necessary to place it in the same 

 family with Amblyopsis and Typhlichthys, while it is as distinctly 

 and widely removed from the Cyprinodontes as are the two blind 

 genera mentioned ? 



Assuming, for the moment, that Chologaster is a transitional 

 form between the surface feeding Cyprinodontes, and Typhlichthys 

 and Amblyopsis, let us recapitulate the characters that distinguish 

 the different forms and see if they exhibit transitions, and if Cho- 

 logaster is traversing the slow developmental road to Ambtyopsis. 



Allowing all characters embraced in the general structure of the 

 skeleton, brain, scales, fins, etc., as" ordinal, and common to both 

 Cyprinodontes and Heteropygii, we will recapitulate only such as 

 can be considered of family and generic value in the two groups. 



CYPRINODONTES. CHOLOGASTER. TTPHLICHTHYS. AMBLYOPSIS. 

 Surface feeders. In part. Unknown. Partially. The same. 



The same. 



The same. 



Viviparous. Many genera. Probably. Probably. Undoubted- 



*y- 



Ovary. Single in vivipa- Single and Single and The same, 



rous genera* placed behind placed at eide 

 and placed by the stomach. of stomach, 

 the side of in- 

 testine in some 

 and posterior in 

 others. 



* The ovary is also single in other genera of viviparous flahes belonging to distinct 

 orders. 



