476 THE DOGFISH CHAP. 



in the male all but the anterior ends of the latter, and in the 

 female the entire ovary ; then carefully dissect away the 

 thick peritoneum covering the kindeys, noting as you do so 

 the dorsal aorta and its various branches, and once again 

 the cardinal veins (C, III, 4), which may be inflated with 

 air. The renal portal veins are not easily traced without 

 injection : this may be done from the cut end of the caudal 

 vein. 

 Note 



1. The brownish kidneys, and in the male the whitish 

 forward continuation of each into the anterior sexual part 

 or epididymis. 



2. In the male : a, the convoluted spermiduct, indistin- 

 guishable from the epididymis anteriorly and enlarging 

 posteriorly to form the elongated seminal vesicle ; and b, the 

 grooved claspers, which are supported by cartilages and 

 have each a gland at the base of the groove. 



II.- Cut through the skin round the vent, and dissect the 

 entire cloaca and the kidneys (together with the epididymes 

 in the male) away from the body, noting as you do so some 

 small paired and median bodies in close relation to the dorsal 

 aspect of the kidneys ; these are respectively the suprarenal 

 and interrenal bodies (p. 447). Pin your dissection down, 

 ventral side uppermost, under water. Clear away with 

 great care the connective-tissue which binds the ureters 

 and generative ducts to the kidneys posteriorly, slit open 

 the cloaca and make out - 



1 . In the male (Fig. 127, A) the aperture of the rectum, and 

 the urinogenital papilla. Insert the small scissors into the 

 aperture at. the apex of the latter, and slit open the urino- 

 genital sinus, continuing the cut into the two sperm-sacs ; 

 make out the apertures of the seminal vesicles and ureter*. 

 Pass a seeker or probe into these apertures (the main ureter 

 may be injected), and then dissect out, on one side a, the 

 elongated and pointed, thin-walled sperm-sac ; and b, the 

 delicate ureters, four of which unite to form a widish 

 common tube, situated towards the inner border of the 

 kidney, before opening into the virinogenital sinus. Sketch. 



2. In the female (Fig. 127, B), the thin-walled anterior 

 united ends . of the oviducts, their thick-walled posterior 

 portion, the shell-glands, the apertures of the rectum and 

 oviducts into the cloaca, and the urinary papilla. Insert 

 the point of the scissors into the aperture on the apex of 

 the latter, and slit open the urinary sinus, in which several 

 openings of the ureters will be seen on either side. Cut 



