486 



COMPARATIVE ANATOMY 



Copulatory Organs. 



Various forms of copulatory organs, morphologically distinct 

 from one another, occur amongst Vertebrates. 



In male Elasmobranchs an apparatus consisting mainly of 

 a specially modified portion of each pelvic fin (claspcr or " mix- 

 opterygium ") serves this purpose (Fig. 365). It consists of a vary- 

 ing number of more or less calcified cartilages, covered by skin and 

 muscles, which are movable upon one another, and most of which 



FIG. 865. PELVIC ARCH WITH SKELETON OF PELVIC FIN AND CLASPERS OF A 

 MALE Chimu>rn moiixtroxa. (After Davidoff.) Ventral view. 



B, pelvic arch with iliac process, Pril ; Mt, basipterygium ; Ret, I\a l , radii of fin ; 

 SB, anterior clasper ; o,f, 1 3, various segments of the posterior clasper. 



arc derivatives of the main and lateral fin-rays : it is provided with 

 a channel along the inner side, and becomes separated from the fin 

 itself in varied degrees in different forms. Its apex is usually 

 naked, but may be provided with one or more movable spines, 

 which in the Spinacidse consist of a curious tissue("chondrodeutin"). 

 These claspers are inserted, in a closed condition, into the cloaca 

 of the female, and thence into the oviducts ; they are then opened 

 out by means of special muscles, and the seminal fluid flows along 

 their channels into the distended oviducts. In connection with 

 this apparatus there is a gland (p. 19) surrounded by muscular 

 fibres, which is formed as an involution of the outer integument 

 and consists of branched tubes. 



