312 



ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



appearing only as a small rudiment in the embryo. The opisthonephros 

 is much elongated in form, lying dorsally, immediately outside the peri- 

 toneal cavity along practically its whole length. The actual renal 



M.d. 



M.cb. 



W.d. 



B 



Fig. 130. 



Diagram of urino-genital organs of the Dogfish {Scyllium), as seen from the ventral side. 

 A, male ; B, female, cl, Cloaca ; M.d, Miillerian duct ; 0, ovary ; od, oviducal gland ; op, opis- 

 thonephros; S.S, sperm-sac; s,v, seminal vesicle; T, testis; «, nreter; u.^.s, urino-genital sinus; 

 v.e, vasa efferentia ; W,d, Wolffian duct. 



function is carried out mainly if not entirely by the hinder half of the 

 organ, the anterior half being in the female reduced to an inconspicuous 

 and vestigial condition, while in the male, where this front portion of 

 the opisthonephros is concerned in the reproductive function, the reduc- 

 tion in size is less marked. 



