Sept. 19, 1872J 



NATURE 



417 



surface, for not only have we in the blind cat fish de- 

 scribed by Prof Cope himself from the subterranean 

 stream in Pennsylvania, an example of a fish belonging 

 to an entirely different family of bottom feeders thriving 

 under subterranean conditions, but the blind fishes of the 

 Cuban caves are of the great group of cod fishes which 

 are, with hardly an exception, bottom feeders. The fact 

 that the food of the blind fishes of the Mammoth Cave 

 consists in great part of the cray fish found in the waters 

 of the cave, as shown by the contents of several stomachs 

 I have examined, and also that one Wind fish at least 

 made a good meal of another fish, as already mentioned, 

 shows that they are not content with waiting for what is 

 brought to them on the surface of the water, and that they 

 are probably as much bottom as surface feeders. 



Again, in regard to sense of sight, why is it necessary 

 to assume that because fishes are living in streams where 

 there is httle or no light, that it is the cause of the non- 

 devclopmcnt of the eye and the development of other 

 parts and organs ? If this be the cause, how is it that the 

 CItologaster from the well in Tennessee, or the " mud 

 fish" of the Mammoth Cave, are found with eyes.' Why 

 should not the same cause make them blind if it made 

 the Ainblyopsis and Typhlichthys blind? Is not the fact, 

 pointed out by Prof Wyman, that the optic lobes are as 

 well developed in Amblyopsis as in allied fishes with per- 

 fect eyes, and, I may add, as well developed as those of 

 Chologaster cornutus, an argument in favour 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 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 ihem to their subterranean 

 life, and that Chologaster is a very interesting transition- 

 ary form between the open water Cypyiiudontcs and the 

 subterranean blind fishes. But is not this assumption 

 answered by the fact that Chologaster has every charac- 

 ter necessary to place it in the same family with Ambly- 

 opsis and Typhlichthys, while it is as distinctly and 

 widely removed from the Cyprinodontes as are the two 

 blind genera mentioned 'i 



If it is by acceleration and retardation of characters 

 that the Heteropygii have been developed from the 

 Cyprinodontes, we have indeed a most startling and 

 sudden change of the nervous system. In all fishes the 

 fifth pair of nerves send branches to the various parts of 

 the head, but in the blind fishes these branches are de- 

 veloped in a most wonderful manner, while their sub- 

 divisions take new courses and are brought through the 

 skin, and their free ends become protected by fleshy papilkc, 

 so as to answer, by their delicate sense of touch, for the 

 absence of sight. At the same time the principle of re- 

 tardation must have been at work and checked the de- 

 velopment of the optic nerve and the eye (which probably 

 exists externally in the young fish), while acceleration has 

 caused other portions of the head to grow and cover over 

 the retarded eye. 



Now, if this was the mode by which blindness was 

 brought about, and tactile sense substituted, why is it 

 that we still have Chologaster Agassizii in the same 

 waters, living under the same conditions, but with no 

 signs of any such change in its senses of sight and 

 touch.' It may be said that the Chologaster did not 

 change because it probably had a chance to swim in 

 open waters, and therefore the eyes were of use, and 

 did not become atrophied. We can only answer, that if 

 the Chologaster had a chance for open water, so had the 

 Typhliehthys, and yet that is blind. 



If the heteropygii have been developed from Cyprino- 

 dontes, how can we account for the whole intestinal canal 



becoming so singularly modified ; and what is there in 

 the difference of food or of life that would bring about the 

 change in the intestine, stomach, and pyloric appendages, 

 existing between Chologaster and Typhlichthys in the 

 same waters .' To assume that under the same con- 

 ditions one fish will change in all these parts and another 

 remain intact, by the blind action of uncontrolled natural 

 law, is, to me, an assumption at variation with facts as I 

 understand them. 



Looking at the case from the standpoint which the 

 facts force me to take, it seems to me far more in accord- 

 ance with the laws of nature, as I interpret them, to go 

 back to the time when the region now occupied by the 

 subterranean streams was a salt and brackish water estu- 

 ary, inhabited by marine forms, including the brackish 

 water forms of the Cyprinodontes and their allies (but 

 not descendants) the Heteropygii. The families and 

 genera having the characters they now exhibit, but most 

 likely more numerously represented than now, many 

 probably became exterminated as the salt waters of the 

 basin gradually became brackish and more limited, as the 

 bottom of this basin was gradually elevated ; and finally, 

 as the waters became confined to still narrower limits, 

 and changed from salt to b.-ackish, and from brackish to 

 fresh, only such species would continue as could survive 

 the change, and they were of the minnow type repre- 

 sented by the Heteropygii, and perhaps some other 

 genera of brackish water forms that we have ^not yet 

 discovered. 



In support of this hypothesis we have one species of 

 the family, Chologaster cornutus, now living in the ditches 

 of the rice fields of South Carolina, under very similar 

 conditions to those under which others of the family may 

 have lived in long preceding geological times ; and 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 de- 

 velopment 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 contine to exist in the subter- 

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

 stone formations caves are quite common, and would in 

 most instances be occupied first with salt water then with 

 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 

 solution 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 

 blind fishes belonging to genera with their nearest repre- 

 sentative in the family a marine form, and with the whole 

 family of cods and their allies, to which group they be- 

 long, essentially marine. Further than this, the cat fish 

 from the subterranean stream in Pennsylvania belongs to 

 a family having many marine and brackish water repre- 

 sentatives. As another very interesting fact in favour of 

 the theory that the Heteropygii were formerly of brackish 

 water, we have the important discovery by Prof. Cope of 

 the LernKan parasite on a specimen of Amblyopsis from 

 the Wyandotte cave ; this genus of parasite crustaceans 

 being very common on marine and migratory fishes, and 

 much less abundant on fresh water species. 



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

 the immutability and early origin of the species of the 

 family of Heteropygii, as we have for their mutability and 

 late development, and, to one of my, perhaps, too deeply 

 rooted ideas, a far more satisfactory theory ; for, with our 

 present knowledge, it is but theory on either side. 



F. W. Putnam 



