THE ELASMOBRANCII FISHES 



301 



FINER ANATOMY OF TESTIS 



The testis is divided into columns, each of which consists of connective tissue 

 and follicular cells. The sex cells appear in various stages of development 

 which may be followed from the indifferent stage, previously mentioned, to 

 the mature sperm cell or spermatozoon. Through division, the primitive ova 



/III' 'i V 



Fig. 260 



Fig. 261 



Fig. 260. Horizontal section cutting testis and anterior part of kidney of Squatina. 

 (From Borcea.) 

 CO., central canal of testis; I.e., longitudinal canal of epididymus; v.e., vas efferens. 



Fig. 261. Section through ovary of Spinax to show corpus luteum (X), which fills the 

 place occupied by the ovum. (From Wallace.) 



of the male form multitudes of spermatogonia, which after a period of rest 

 form spermatids. The spermatids next undergo an interesting series of 

 changes in shape and form, becoming the adult spermatozoa. 



VASA EFFEEENTIA 

 O 



The sex cells in the male instead of passing into the body cavity and out at the 

 abdominal pores, as they do in the Cyclostome fishes, pass out through the 

 Wolffian duct, now called the vas deferens, which they reach through the vasa 

 eff'erentia. The vasa efferentia arise as metamorphosed tubules of the anterior 

 segmental ducts. Those ducts in the region of the sex glands of the male have 

 some of their funnels opening into the tissues of the testis or into the central 

 canal at its base and afford a passageway for the sex cells. 



A horizontal section through the testis and anterior part of the kidney of a 

 young Squatina (fig. 260) shows that the segmental ducts themselves thus 

 become the efferent ducts or vasa efferentia within the tissues of the testis; 

 the parts of the nephrostomes representing the funnels fuse to form a central 

 canal {c.c.) while the median vesicles of the segmental ducts similarly join the 

 kidney to form the longitudinal canals {I.e.) of the epididymus. From this 

 canal a connection is effected, through collecting tubules, with the Wolffian 



