TRANSACTIONS OF SECTION D. 685 



3. Oysters and the Oyster Question. 

 By Professor W. A. Heudman, i^.i?.,S'.— See Reports, p. 363. 



4. The Amblyopsidce, the Blind Fish of America. 

 By Dr. C. H. Eigenmann. 



The underground regions of North America are inhabited by a number of 

 blind aquatic vertebrates. 



These are TypMomolge from Texas, Typhlotriton from Missouri, Gronias 

 nigrilahris from Pennsylvania, Amblyopsis spelceus from Kentucky aud Indiana, 

 Typhliehthys subterraneus from Kentucky, Alabama, and Indiana, and an 

 undescribed species, Typhliehthys rosce, from Missouri. 



A considerable area of South Central Indiana is drained entirely by imder- 

 ground streams in which Amblyopsis is abundant. 



It has the general appearance of skinned catfish, is well balanced in the water, 

 and has broad fins. 



The chief points of interest in Amblyopsis are the eyes, the skin, and the 

 tactile organs. Since, however, all the published accounts concerning this fish are 

 more or less worthless, some other points of interest may be mentioned. 



Amblyopsis has been recorded as a surface feeder, but it secures its food at the 

 bottom. Its abundant tactile organs about the head enable it to exactly locate a 

 crawling or moving object if a short distance from its head. A rod held in the 

 hand is readily perceived by the slight vibrations when the fish is about an inch 

 away. A young one reared in the light was able invariably to perceive the direc- 

 tion a rod was approaching it, and to swim intelligently away. 



Although the eyes are entirely incapable of receiving impressions, the fish reacts 

 negatively to light. This reaction is not caused by any particular colour of the 

 spectrum. It is not a matter of heliotropism, for the direction of the light has- 

 nothing to do with the reaction. 



The eye in the adult has no connection with the brain. The lens is composed 

 of a few inconspicuous cells. The vitreous humour is gone, and the eye, in conse- 

 quence of the absence of a hyaloid, vitreous body, and practically the total absence 

 of a lens, has collapsed, so that the ganglionic layer forms a solid core of cells. The 

 inner reticular layer is well developed. The layers outside of this to the external 

 limiting membrane have been reduced to a layer of cells about two deep. The pig- 

 ment has in some of the best eyes retained its normal thickness. Cones are pre- 

 sent. The sclera is represented by one or more cartilaginous masses. 



In the number and arrangement of the tactile organs it is not materially difierent 

 from Chologuster, which can certainly see. 



The steps of degeneration can be followed by comparing the eyes of Zygonectes, 

 Chologaster, Typhlogobius, and Amblyopsis. The lens is the last to be affected, but 

 when it once begins it degenerates very rapidly, disappearing in some cases during 

 the life time of an individual, e g., Typhlogobius. 



Amblyopsis is universally considered as viviparous. This it is not. The female 

 lays the eggs under her own gill-covers, which are very wide. Here the young- 

 are reared through their larval stages. When the female at this time is handled 

 the young will squirm out. This fact has given rise to the supposition that the 

 fish is viviparous. 



The absence of pigment causes the blood to give Amblyopsis a yellowish tint itt 

 the thinner parts, such as the fins, while in the thicker parts the colour is pink. 



Pigment cells are abundant in the larva, and are not at all rare in the skin of 

 the adult, but they contain little pigment. 



It is a matter of general observation that the pigment diminishes in the absence 



