American Quarterly Microscopical Journal. 



" Go forth, under the open sky, and list 

 To Nature's teacliings." — Bryant. 



Vol. I, NewYork, July, 1879. No, 4, 



ON SOME SENSORY STRUCTURES OF YOUNG 

 DOG-FISHES. 



BY PROFESSOR S. A. FORBES. 



{^Received June 2d, iSjg.) 



Clusters of cells, similar to those of the lateral line of larval am- 

 phibia, appear in the skin of the head of many young fishes. 

 Small cat-fishes furnish good examples of these, the barbels, es]:)e- 

 cially, being richly provided with them. In the young dog-fish 

 {Atnia calva, L.) of the Mississippi Valley they are unusually well 

 developed ; and, as they have not hitherto been studied in this 

 fish, nor, as far as I can learn, in any of its allies, a description of 

 their structure may have some value, as they present peculiarities 

 which I have not noticed elsewhere. 



The material studied was derived from the smallest specimens 

 of this genus of which I have any knowledge, taken in the Illinois 

 River, at Peoria, in June, 1878, and ranging from 17"""- to 25"""- 

 in length. These specimens were carefully preserved in 87 per 

 cent, alcohol, but without special reference to histological work. 



As the young Amia has not been figured, a sketch of it is given 

 herewith (Plate XIX., Fig. i). In specimens of this size, the skin 

 of the front, top and sides of the head (including the lower jaw) 

 is closely dotted with minute white specks, which extend back- 

 ward to the posterior border of the opercle and downward to the 

 branchiostegal membrane, but are wanting on this membrane, on 

 the throat and between the rami of the mandible. In other words, 

 they were distributed over those parts of the integument most ex- 

 posed to first contact with objects, as the fish swims about. (See 

 the dotting of the head of the figure.) They are largest and 



