9. THE REPRODUCTIVE SYSTEM 



99 



transformed into a pair of long sausage- 

 like outgrowths stretching far back from 

 their point of attachment near the dia- 

 phragm. Simultaneously, the peritoneal 

 cells on their surface multiply at the 

 same rate and so come to form the 

 ovarian walls. Longitudinal blood ves- 

 sels run inside these walls from the 

 region of attachment of the ovaries and 

 supply the growing germ cells with food 

 substances and oxygen (Figs. 33, 68). 



The peritoneal epithelium which 

 covers the surface of the ovary consists 

 mainly of small flat cells. Under them 

 lies a thin basement membrane con- 

 tinuous with the intima of the ovarian 

 blood vessels. The inner surface of the 

 membrane lacks cellular elements, but 

 the blood vessels are covered on all sides 

 with tall cells, sometimes arranged in 

 more than one layer (Fig. 68). 



I have already remarked that the 

 number of blood vessels in each ovary 

 varies in different species, in accordance 

 with the size of the animal, from two to 

 five. In Siboglinum and Oligobrachia one 

 vessel runs along the dorsal side and one 

 along the ventral side of the ovary (Fig. 

 33). InPolybrachia annulata and Lamell- 

 isabella zachsi a third latero-ventral 



Fig. 66. Diagram of the female reproductive system 

 of Pogonophora. On the right side of the figure the 

 funnel and the oviduct are shown stereographically. 

 сое II - mesocoele ; сое HI - metacoele ; di - mus- 

 cular diaphragm; epi - wall of funnel of coelo- 

 moduct; epo - peritoneal wall of ovary; gon - 

 ocgonia ; gp - genital aperture ; in/ - funnel of 

 coelomoduct; о -egg; ov - ovary; ovd- oviduct; 

 smt - somatopleura ; spl - splanchnopleura ; ts - 

 spongy coelomic tissue; vd- dorsal blood vessel.- 

 (After Ivanov, 1958a.) 



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