XIII 



PHYLUM CHORDATA 



195 



The optic nerves (Nv.2) form a chiasma. The pineal body (pn. &.) 

 is a small rounded vesicle borne on a hollow stalk (pn. s.) which 

 runs just outside the posterior 

 wall of the tent-like choroid 

 plexus. The pituitary body (pty.} 

 consists of intra- and extra- 

 cranial portions, the former 

 lodged in the sella turcica, the 

 latter in the pit already noticed 

 on the ventral or external face 

 of the skull-floor (Fig. 850, pt.). 

 In advanced embryos the two 

 are united by a delicate strand 

 of tissue. 



Urinogenital Organs. The 

 kidneys (Fig. 852, kd.) are lobed, 

 deep-red bodies, like those of 

 the Dog-fish, but shorter and 

 stouter. In the male they are 

 much longer than in the female; 

 the anterior portion is massive, 

 and consists mainly of a mass 

 of true renal tubules; it is in- 

 distinctly divided into segments: 

 the posterior portion is narrower 

 and also indistinctly segmented ; 

 from both parts arise a number 

 of ducts (mesonephric ducts) 

 the majority of which open into 

 the vas deferens, while the last 

 six open into the urinogenital 

 sinus. In the female the ducts 

 all open into a rounded median 

 diverticulum of the cloaca, the 

 urinary bladder or urinary sinus, 

 situated between the two ovi- 

 ducal apertures. The female 

 reproductive organs are also 

 constructed on the Elasmo- 

 branch pattern, and are chiefly 

 noticeable for the immense size 

 'of the shell-glands and of the 

 uteri. But the male organs 

 present certain quite unique 

 characters. The testcs (ts.) are 

 large ovoid bodies the tubules of 

 which apparently do not contain 



FIG. 852. Callorhynchus antarcticus. 



A, male urinogenital organs of left side- 

 ventral aspect ; B, anterior part of vesicula 

 seminalis in section, d. cloaca; epid. epi- 

 didymis ; kd. kidney ; muL d. Miillerian 

 duct ; j sph. spermatophores ; ts. 'testis ; 

 u. y. x. ririnogenital sinus ; v. df. vas de- 

 ferens ; vs. sem. vesicula scrninalis. (A, 

 after lledeke.) 



N 2 



