Litermy Notices. Ixxi 



ally in Typhlogobius, — possibly in the excess of pigment in the iris 

 and pigment layer of the retina, and particularly in its occasional 

 presence in the hyaloid membrane of the Typhlogobius eye, while no 

 evidence of actual degeneration in the retina appears in connection 

 with these. The possible case of a degenerating retma in Typhlogo- 

 bius is neglected in this consideration, since, as pointed out, the lens 

 being absent in the same eye, it is immaterial whether it be consid- 

 ered or not. 



THE INTEGUMENTARY SENSE PAPILLAE. 



1. These have been considered only so far as pertains to the 

 question whesher they have been developed to compensate the rudi- 

 mentary condition of the eyes ; and it is concluded that such is not 

 the case. 



2. The facts that lead to this conclusion are the presence in 

 several closely related genera — four at least — of the tactile papillae 

 with the same distribution as those of Typhlogobius, and in addition 

 to this, on parts of the body where they are not found at all in Typh- 

 logobius, excepting in the smallest specimens and that the papillae that 

 are present in Typhlogobius are not more highly developed than 

 those of corre sponding regions in related genera. 



3. In comparing the several species of blind fishes with a view 

 to determining under what conditions the tactile sense does become 

 developed to compensate the loss of sight, it is concluded that, while 

 the greater activity of the cave blind fishes might explain their more 

 highly developed tactile papillae, this cannot be affirmed as a general 

 law, since other blind fishes (as some at least of the deep-sea forms 

 and probably also the blind Silurids) are without tactile papillae, while 

 we have no reason to suppose them less active than the cave fishes. 

 It is necessary to have more knowledge than is yet possessed of the 

 mode of life of the various blind forms before this question can be 

 fully answered. 



THE INTEGUMENT. 



1. This structure has been studied with reference to the pigment 

 contained in it, and the pink color of the living fishes. 



2. Very nearly if not fully as much pigment is present tn the 

 largest as in the smallest specimens, the lighter color of the former 

 being due to the obscuration of the pigment by a thickening of the 

 sub-epidermal tissue between the pigment and the epidermis. 



3. The pink color of the living animals is due, in great part at 

 least, to a highly abnormal development of blood-vessels in the sub- 

 epidermal portion of the integument. 



