154 



ANNELIDA 



[CH. 



twelve from segment thirteen, and they are formed by the accu- 

 mulation and growth of some of the cells which cover this septum, 

 that is, from cells lining this portion of the coelom. 



If one of the ovaries be removed and examined under a 

 microscope it will be seen that many of the cells composing it are 

 large, spherical and crowded with granules. The largest lie in the 

 narrow end of the ovary which waves about in the coelomic fluid. 

 These cells are the full-grown eggs or ova and when ripe they drop 

 off from the ovary into the coelom, but are probably at once taken 

 up by the wide funnel-shaped openings of the oviducts, one of 

 which is situated opposite each ovary. Like the nephridia, the two 



7 



FIG. 64. View of reproductive organs of the Earthworm, Lumbricus terrestris. 

 Part of the vesicula seminalis is cut away on the left side to expose the 

 testis and the inner opening of the vas deferens. Slightly magnified. 

 From Hatschek and Cori. 



1. Spermathecae. 2. Funnel-shaped internal openings of the vas deferens. 

 3. Anterior testis. 4. Vesioulae seminales. 5. Ovary attached to 

 posterior wall of septum separating xn and xiu. 6. Oviduct traversing 

 septum separating xm and xiv. 7. Vas deferens. 8. Glands in the 

 skin. 9. Ventral nerve-cord. 10. Septum. 



The Roman figures indicate the number of the segments. 



oviducts pierce a septum, the one between the thirteenth and the 

 fourteenth segments. They are short tubes which open into the 

 coelom by the above-mentioned funnel-shaped opening in the thir- 

 teenth segment and to the exterior by a small pore just outside the 

 inner pair of setae on the fourteenth (6, Fig. 64). They bear on 

 their course a diverticulum or sac which is called the recepta- 

 culum ovorum, in which the ova collect until the earthworm 

 is ready to make a co-coon to receive them. 



The male reproductive cells are formed in the testes, of which 

 there are two pairs situated in a similar position to the ovaries but 

 in the tenth and eleventh segments (3, Fig. 64). They are in many 

 respects similar to the ovaries but are hand-shaped, the broad end 



