1922.] 



S. I,. Hora : Fish of Mountain Torrents. 



47 



posterior lip. The anterior labial fold (a) is fringed and tubercu- 

 lated and helps the fish in adhering to rocks. A rudimentary 

 form of disc has recently been described by me x in Parapsilo- 

 rhynchus discophorus. 



The disc of Garra works on the suction principle. In the 

 middle of the under surface of the callous portion, a strong 

 tendon (fig. 96, i) is inserted and attached to the urohyal (/), so 

 that when the urohyal is elevated, the callous portion of the disc 

 is drawn in and thus a cavity is produced which is surrounded by 

 fringed borders. These fringed and tuberculated borders are pro- 

 vided with efficient organs of adhesion as will be seen later when 

 dealing with the minute structure of the adhesive organs. 



..Cts. 



Text-fig. 9 — The disc of Garra and its associated structures. 



a. Disc as seen from the under surface. 



b. Dissection of disc from the dorsal surface to show the mechanism 



for suction. 



a = anterior labial fold ; h, V = anterior jaw ; e = mouth opening ; d ■=■ poste- 

 rior jaw ,- g= connectives ; f, f'= posterior labial fold; g,g' = {ree tuberculated 

 border of the disc; h = callous portion of the disc; j = tendon joining the centre 

 of the callous portion of disc with urohyal ; j = urohyal ; k = muscle joining the 

 two sides of the anterior jaw. 



THE MINUTE STRUCTURE OF THE ADHESIVE 

 APPARATUS. 



The simplest form of adhesive apparatus is found among 

 hill-stream fishes of the order Cyprinoidea. It consists of the 

 thickened skin covering the under surface of the few outer rays 

 of the paired fins. In a transverse section of such a structure 

 in Bhavania annandalei (fig. 10) the following arrangement may 

 be seen: — The epidermis consists of several tiers of cells, varying 

 in shape and size with their depth and resting on a loose connec- 

 tive tissue (ct.), which constitutes the dermis. The outer epider- 

 mal layer is modified into stiff and strong spine-like processes (s), 

 which are somewhat curved near their extremities. The inner 

 limit of these processes is not well-defined and they appear to rest 



Hora, Rec. hid. Mus. XXII, pp. 13-10, figs. (192 1). 



