364 Mr. R. Hill's Cuntributiotis to the 



side, respectively uamed the depressor, the elevator, the adductor, 

 and the expansor of the fin. Though the claspers are without 

 muscular apparatus calculated to approximate them, when out- 

 stretched (for they recover their place after expansion only by 

 their own elasticity), they are notwithstanding supposed by some 

 naturalists to perfomi all the offices of prehension, by the action 

 and pressure of the ventral fins, with which they are conjoined. 



Dr. John Davy has examined and compared these members 

 with great minuteness. Though he describes them carefully, he 

 is doubtful of their functional purpose. We shall quote his 

 remarks at length : — 



" Before entering on the infei-ences to be di-awn from the re- 

 lative functions of the difi^erent parts constituting the male organs, 

 which are contained within the abdominal cavity, I would wish 

 to offer a few remarks on the external accessoi-y organs, which 

 have commonly been considered auxiliary to the more important 

 internal ones. They are the anal appendages, which are cha- 

 racteristic of the male Cartilaginous Fishes, organs of complicated 

 and curious structui'e, the use of which at present is far from 

 being vmderstood. 



" The Torpedo, the common Ray, and the Thornback, are the 

 only species of Ray which I have yet carefully examined in rela- 

 tion to the organization of these parts. In each species they are 

 veiy similar, consisting of articulated bones, muscles, mucous 

 ducts, &c., and containing a large and remarkable gland, asso- 

 ciated with an elaborate and complicated structure. 



" On account of the large size of the Ray, and its large anal 

 appendages and their full development, the gland and its accom- 

 paniments are seen in this fish to great advantage. In two 

 specimens of Raia batis which I have examined, each about three 

 feet long, the gland was neai'ly the size of a chestnut of a very 

 elongated oval form, divided on one side, as it were, into two 

 columns by a superficial fuiTOw or depression, in which were two 

 rows of delicate projecting tubuli, the extremities of its excretory 

 ducts. 



" The substance of the gland was enveloped in a muscular 

 coat, and this was covered with a vascular tissue. The gland 

 itself was contained in a sac, composed of three coats, an inner 

 fibrous, a middle muscular, and an outer cellular one, and was 

 surrounded with strong muscles, the principal flexor and extensor 

 muscle of the organ. 



" Moreover, at the inferior extremity of the sac, just below its 

 outlet, was a distinct cavity formed of muscular walls, and inter- 

 sected by delicate tendinous fibres. In one instance, when under 

 examination, the fish was still irritable, its muscles acting when 

 stimulated ; and then this part pulsated regularly and vigorously. 



