169 



pygii, and perhaps some other genera of brackish water 

 forms that have not yet been discovered. 



In support of this hypothesis we have one species of the 

 family, C/iologaster cornutus, now living in the ditches of 

 the rice fields of South Carolina, under very similar con- 

 ditions to those under which others of the family may have 

 lived in long preceding geological times ; arid to prove 

 that the development of the family was not Brought about 

 by the subterranean conditions under which some of the 

 species now live, we have the one with eyes living with 

 the one without, and the South Carolina species to show 

 that. a subterranean life is not essential to the develop- 

 ment of the singular characters which the family possess. 



That a salt or brackish water fish would be most likely 

 to be the kind that would continue to exist in the subter- 

 ranean streams, is probable from the fact that in all lime- 

 stone formations caves are quite common, and would in 

 most instances be occupied first with salt water and then 

 brackish, and finally with fresh water so thoroughly im- 

 pregnated with lime as to render it probable that brackish 

 water species might easily adapt themselves to the change, 

 while a pure fresh water species might not relish the solu- 

 tion of lime any more than the solution of salt,,and we 

 know how few fishes there are that can live for even an 

 hour on being changed from fresh to salt, or salt to fresh, 

 water. We have also the case of the Cuban blindfishes 

 belonging to genera with their nearest representative in 

 the family a marine form, and with the whole family of 

 cods and their allies, to which group they belong, essen- 

 tially marine. Further than this the catfish from the 

 subterranean stream in Pennsylvania belongs- to a family 

 having many marine and brackish water representatives. 



Thus I think that we have as good reasons for the belief 

 in the immutability and early origin of the family of Het- 



ESSEX INST. BULLETIN. HI 22 



