80 BULLETIN OF THE 



through a long course of evolution, would furnish an excellent test of 

 this belief. The eye here studied throws very little light on the question, 

 however, — scarcely as much as does that of other known functionless 

 eyes. But when we consider together the facts presented by the eyes of 

 ]\Iyxine, Typhlogobius, Proteus, and Talpa, and possibly also Ambly- 

 opsis and Gronias, this much seems quite certain : that the lens disap- 

 pears before the retina ; and that, where degeneration takes place at all 

 in ontogeny, the lens is affected first and most profoundly, as seen in 

 Proteus, and pi'obably also exceptionally in Typhlogobius. Supposing 

 the somewhat doubtful instance of a degenerating retina presented by 

 the eye shown in Figure 19 to be genuine, we still have reason to be- 

 lieve that its degeneration has been preceded by that of the lens, since 

 the latter body is undoubtedly absent in this specimen. There can 

 scarcely be a doubt, from physiological reasons, that the retina is consid- 

 erably older, phylogeneticalh', than the lens, even though it can hardly 

 be said to be so ontogenetically. 



The Integumentary Sense Organs. 



At present T treat this subject no further than pertains to the question 

 whether the loss of sight in Typhlogobius has been compensated by 

 an unusual development of the sense of touch, leaving the consideration 

 of any morphological significance that the sense papilla) may have with 

 the hope that they may be studied developmentally at some future 

 time. 



From the testimony of numerous writers, there is no doubt that 

 compensations for such loss by the super-development of the other spe- 

 cial senses, hearing, smell, and touch, are common among animals 

 both invertebrate and vertebrate. For a discussion of this subject see 

 Packard ('86, pp. 123-130). 



My conclusion with reference to the tactile sense in Typhlogobius 

 is, that in all probability it not only has not increased, but has actu- 

 ally diminished ^rart passu with the diminution of the power of sight. 

 The reasons for tliis conclusion are that several — at least four — 

 genera of the Gobiidje closely related to Typhlogobius are as well 

 provided with tactile papillae as is the blind fish, these organs being 

 considerably more numero\is and moi'e widely distributed on different 

 parts of the body in the other fishes than in Typhlogobius. The 

 genera to which I refer are Gobius, Gobiodon, Lepidogobius, and Cleve- 

 landia. The last two I have examined myself. The arrangement and 



