XIII 



PHYLUM CHORDATA 



195 



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



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- 

 i I [ 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 



Icidneys (Fig. 852, M.) 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 uritiary sinus, 



situated between the two ovi- 



ducal apertures. The female 

 Vi'il reproductive organs are also 



constructed on the Elasmo- 



branch pattern, and are chiefly 



noticeable for the immense size 



' > I of the shell-glands and of the 



I t j I uteri. But the male organs 



present certain quite unique 



lift characters. The testes (ts.) are 



; ;i large ovoid bodies the tubules of 



. 5 1 which apparently do not contain 



Fig. 852.— Callorliynchus antarcticus. 



A, male urinogenital organs of left sidc- 

 veiiti-al aspect ; B, anterior part of vesioula 

 seminalia in section. cL cloaca ; epid. epi- 

 didymis ; kd. kidney ; mul. d. MiUlerian 

 duct ; , sph. spermatophores ; ^s. 'testis ; 

 n. [f. H. urinogenital sinus ; v. df. vas de- 

 ferens ; V8. sem. vesicula eeuiinalis. (A, 

 after Redeke.) 



N 2 



