164 



BIOLOGY 



exterior. The openings of the reproductive organs may be 

 seen in Figure 74. 



Male reproductive organs. In the tenth and eleventh seg- 

 ments there is a pair of glands, the spermaries, sp } in which 

 are formed the male reproductive elements. In these two seg- 

 ments their position corresponds to the position of the ovary 

 in the thirteenth segment. They are very small glands and 

 can only be seen by microscopic examination. Behind each 



of these sperm glands 

 is a funnel-shaped, cili- 

 ated opening, leading 

 into a tube which 

 passes through the 

 septa into the next seg- 

 ment, where it is slightly 

 coiled, and then passes 

 backward. The tubes 

 from the two sperm 

 glands on each side 

 unite with each other 

 in the twelfth segment 

 to form a single duct, 

 which passes back 

 through the septa to the 

 fifteenth segment, where 

 it opens through the 

 body wall to the exte- 

 rior. This duct is known 

 as the vas deferens 

 (Lat. vasa = vessel + 

 deferens = carrying 

 down); Fig. 80 vd. In the ninth, tenth, and eleventh seg- 

 ments are large sacs known as seminal vesicles, sv, which serve 

 as a storehouse for the secretion of the sperm glands, before 

 these secretions pass to the exterior through the vas def- 



FIG. 80. DIAGRAM SHOWING THE REPRO- 

 DUCTIVE SYSTEM OF THE EARTHWORM 



The numbers represent the number of segments. 

 es, egg sac; sr, seminal receptacles; 



ne, nephridia; 

 ovary; 



sv, seminal vesicles; 

 DC, ventral nerve cord; 



vd ' vas deferens ' 



