1008 



Fig. 537. 



Viscera of male Shark. (After Clift.) 

 a, heart ; b, liver ; c, oesophagus ; d, stomach ; e, 

 pyloric portion of stomach ; g, pancreas ; h, i, in- 

 testine ; k, testis ; I, vas deferens ; m, urinary blad- 

 der j o, rudimental penis ; p, p, peritoneal open- 

 ings ; q, q, claspers. 



troduced into the cloaca of the other sex in the 

 act of impregnation. The following is Cuvier's 

 description of these remarkable organs, which 

 are met with in the males both of the Sharks 

 and Rays and likewise of the Chimseras, and 

 from the composition and relations of the car- 

 tilages and muscle which enter into their struc- 

 ture are evidently only an extension or appendage 

 of the ventral fins. They consist in the Rays 

 and Skates of two cartilages articulated end to 

 end, situated along the inner side, which forms 

 the basis of the whole apparatus. The first of 

 these cartilages, which is a sort of femur, ar- 

 ticulates with the pelvis, and supports, in con- 

 junction with the second (the tibia), the rays 

 of the ventral fin. 



A third cartilage unites this fin with the 

 genital portion like a kind of astragalus ; this 



PISCES. 



articulates with the longest cartilage of the 

 Jimb. 



On the side of the astragalus is an oval car- 

 tilage having a sharp inferior margin, to which 

 may be applied the name of os calcis. 



The os calcis articulates posteriorly with 

 another principal piece of the limb which may 

 be called the metatarsus. This extends all 

 along the upper and inner border of the limb 

 as far as its extremity, where it forms a sort of 

 digit, to which is attached the tendon of the 

 great abductor muscle. This large piece is 

 formed by the consolidation of three smaller 

 ^ ones, two of which run parallel to each other, 

 so as to constitute a semi-canal, into which 

 opens a duct derived from a large gland here- 

 after to be described. 



To the metatarsus succeed seven other car- 

 tilages, the shape of which is different in the 

 various species of Chondropterygii, but which 

 obviously represent the phalanges of the abdo- 

 minal limb, which is moved by five strong 

 muscles which may be named respectively the 

 depressor, the elevator, the abductor, the ad- 

 ductor, and the expansor of the fin. It is, 

 however, remarkable that there is no muscular 

 apparatus calculated to approximate these 

 members, and when separated they are brought 

 together again entirely by their own elasticity, 

 a circumstance which militates strongly against 

 their being, as is generally supposed, instru- 

 ments of prehension. In the Sharks the clas- 

 per contains morever a gland of considerable 

 size situated beneath the fin, and extending to 

 the exterior of the base of its genital append- 

 age. Inferiorly, this gland is only covered by 

 the skin, while above it is adherent by the in- 

 tervention of cellular tissue to the rays of the 

 fin. Its duct is a wide canal which opens into 

 the groove formed by the metatarsal cartilages 

 above alluded to, and the fluid which it secretes 

 of a highly viscid character. It is said that in 

 the breeding season the contents of this gland, 

 as well as the parietes of the cavity in which 

 it is situated, are red with blood and appear to 

 be in a remarkable state of turgescence. It is 

 enclosed in a double tunic, one fibrous and the 

 other muscular, by the assistance of the latter 

 of which its contents are evacuated. 



At the lower extremity of this gland, near its 

 orifice, there is in each clasper a capsule with 

 muscular and cavernous parietes, the cavity of 

 which is traversed by slender tendinous fila- 

 ments. In these sacs Dr. John Davy* has ob- 

 served distinct pulsations, and finding that in 

 the living fish they were filled with blood, con- 

 siders them as accessory hearts destined to 

 assist the circulation of the blood in these 

 appendages to the genital system. 



The gland itself is of the shape of an olive ; 

 a longitudinal sulcus divides it into two por- 

 tions, in each of which a transverse series of 

 very delicate tubes is distinguishable. 



In the females of the Plagiostome Chon- 

 dropterygii the arrangement of the sexual or- 

 gans conforms in an equally striking manner 

 with the Reptilian type of structure. The 



* Phil. Trans. 1839. 



