SEXUAL PHASE IN INDIAN NAIDID.^.. 



461 



when distended with the male products, may reach as far back as 

 segment xii. The vas deferens, one on eacli side, is a short tube 

 with only a single bend ; in diameter it is 15 jji, except where it 

 joins the atrium, wdiere it is only 9 /x ; it has a uniform lining 

 of cubical ej^ithelial cells. It passes vertically downwards from 

 the funnel on the posterior face of septum 5/ti, and then after a 

 slight bend enters the atrium on its anterior aspect close to the 

 origin of the ejaculatory duct. 



The neck of the male funnel lies in the mouth of the sperm- 

 sac (seminal vesicle). The funnels fill up the mouth of the sac, 

 and are directed upwards and l)ackwards just within it ; they 

 meet each other in the middle line above the gut by their inner 

 margins, and their outer surfaces are fused with the contiguous 

 part of the wall of the sac. Tliey are cup-shaped, with everted 

 lips, and are lined by columnar ciliated cells with prominent oval 

 nuclei at the base. The greatest diameter of the funnel is 

 about 45 ft. 



The atria are ovoid chambers with their long axes vertical, 

 lying one on each side of the seminal vesicle in segment vi. Each 

 is 80-90 )w, in height and 45-50 yu, in breadth, and is lined by an 

 epithelium of cubical cells with indistinct outlines and con- 

 spicuous nuclei ; outside the epithelium is a thin coat of circular 

 muscular fibres, outside which again the peritoneum is indicated 

 by a few scattered nuclei. The lumen may contain spermatozoa 

 or only a little coagulum_. The ejaculatory duct is short, 

 about 30 fi ; its epithelium consists of closely packed columnar 

 cells with large peripherally situated nuclei ; it has a fairly thick 

 investment of circular muscular fibi'es. The duct may be in- 

 vag'inated into the base of the atrial cavity ; it opens to the 

 exterior in the depth of a short tubular depression of the ventral 

 body-wall, about 15 /x in length, which is narrower at the surface, 

 a,nd broader above, where it receives the duct. There are no 

 " prostatic" cells in connection with vas deferens or atrium. 



A thick band of muscle-fibres runs vertically upwards from the 

 ventral body-w^all, lying internal to the atrium and supporting 

 the setal sac containing the penial seta^. 



The ovisac, formed by the backward bulging of septum 6/7, 

 surrounds the sperm-sac which lies within it. It may reach back 

 to segment x,vi. ; it contains a large mass of yolk granules, which 

 stain faintly with eosine ; and in its hinder part a number of 

 ova. The septa of the several segments behind the seventh 

 retain a transverse position betw^een the body-wall and the ovi- 

 sac, fusing closely with the peiiphery of the latter. Large 

 blood-vessels are seen closely applied to the sperm-sac and inner 

 face of the ovisac. 



The female funnels are attached to the anterior face of septum 

 6/7 near the ventral j^ai-ietes ; the cells lining it are small, and 

 appear to be modifiecl peritoneal cells containing little else than 

 nuclei. In one specimen the funnels were seen to open on the 

 ventral surface at about the level of septum 6/7. They are seen 



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