CHAPTER III. 



THE BLIND FISHES OF THE MAMMOTH CAVE AND THEIR 



ALLIES.* 



BY F. W. PUTNAM. 



THE blind fish of the Mammoth Cave has from its discovery 

 been regarded with curiosity by all who have heard of its exis- 

 tence, while anatomists and physiologists have considered it as one 

 of those singular animals whose special anatomy must be studied 

 in order to understand correctly facts that have been demonstrated 

 from other sources ; and, in these da} T s of the Darwinian and devel- 

 opment theories, the little blind fish is called forth to give its tes- 

 timony, pro or con. 



Before touching upon this point, however, we must call attention 

 to the structure of the fish and its allies, and to others that are 

 either partially or totally blind. 



In the lancelet (Branchiostoma) and the hag (Myxine) the eye 

 is described "as simple in form as that of a leach, consisting sim- 

 ply of a skin follicle f coated by a dark pigment, which receives the 

 end of a nerve from the brain." Such an eye speck as this struc- 

 ture gives would only answer for the simple perception, of light. In 

 the young J of the lampreys (Petromyzon) the eye is very small and 



* From the AMERICAN XATTRALIST for January, 1872. 



t Sae further on where Prof. Wyinan questions this structure. 



t These young lampreys have been described under the generic name of Ammocoetes, 

 and it was not until 1S.36, when Prof. Miiller discovered the fact of a metamorphosis in 

 the lampreys, that their true position was ascertained. Prof. Miiller has traced the 

 history of the common European species and shown that it is three or four years in 

 attaining its perfect form. With this fact before us and with the early stages of the 

 Myxinoids still unknown, have we not some reason for suspecting that the Lancelet may 

 yet prove to be a larval form of the Myxinoids, notwithstanding that it is said to lay 

 eggs ? Why should we not suspect the existence in the very lowest vertebrates of some- 



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