ANNELIDA : THE EARTHWORM, NEREIS 227 



Earthworms are hermaphrodite, every individual having a 

 complete set of organs of each sex. The female 



Reproduction. r . , , . , ° . , i 



organs include the ovaries, oviducts, and sper- 



mathecae. The ovaries are two small, pear-shaped bodies 

 hanging into the coelom of the thirteenth segment from the 

 septum in front of it. Each ovary is a local thickening of 

 the coelomic epithelium. The broad end of the pear is 

 attached to the septum and contains a fused mass of unripe 

 ova. Maturation divisions take place at the base of the 

 stalk, which contains the ripe eggs. These fall from it into 

 the body cavity 



and are taken d.b.v. 



up by the ovi- .*«SS$SMMxW^ a ff-i- v - 



ducts, which x^^^ 5 ^/^^^-^-"- 



open by wide 

 funnels into the 

 ccelom in the 

 thirteenth seg- 

 ment, pass 

 through the sep- 

 tum behind, and 

 open to the ex- 

 terior in the 

 fourteenth. In 

 the latter seg- 

 ment, each bears 

 a swelling, the 

 receptaculum 

 ovorum or egg 

 sac, in which 



the eggs are stored. The spermathecce are two pairs 

 of small, round sacs which lie in the ninth and tenth 

 segments and open in the grooves behind them. Their 

 function is to receive sperm from another worm. The 

 male organs consist of testes, vesicular seminales, and vasa 

 deferentia. These testes are two pairs of small, flat, finger- 

 lobed bodies attached to the hinder side of the septa in 

 front of segments 10 and 11. They are local thickenings 

 of the ccelomic epithelium like the ovaries, to which they 

 correspond in position. The testes bud off cells known as 

 sperm-mother-cells, which give rise to spermatozoa in the 



Fig. 



144. — A diagram of a transverse section of 

 the earthworm in the intestinal region to show 

 the arrangement of the blood vessels. Letter- 

 ing as in Fig. 143. 



