A Segmented Worm — Earthworm 389 



to XI which connect the dorsal and ventral vessels, (4) a subneural vessel 

 beneath the ventral nerve cord, (5) two lateral neural vessels on either 

 side of the nerve cord, (6) numerous branches from the vessels with 

 their thin-walled capillaries (kap'ilari) (L. capillaris, hair) to supply 

 all body parts. The blood is propelled through the vessels by the peri- 

 staltic contractions of the hearts and dorsal blood vessel, thus forcing it 

 from the posterior part of the dorsal vessel toward the anterior end. 



Testis ^ 



X- 



Vas deferens- - 



Ovary 



Oviduct 



XV- 



^<]<j Sac 



Seminal 

 receptacle 



Sewinal 

 vesicle 



Fig. 189. — Earthworm reproductive system with the seminal vesicles on the left 

 dissected to show the male and female organs (see Fig. 185). 



OPENINGS OF SEMINAL RECEPTACLES- 2 PAIRS 

 OPENING OF VASA OEFERENTIA-I PAIR 



ENCASING TUBE 

 [ (CLITELLUM 



OPENINGS OF SEMINAL 



RECEPTACLES 



CLITELLUM 



SEMINAL CHANNELS 



OPENINGS OF VASA DEFERENTIA-I PAIR 



Fig. 190. — Reproduction in earthworms by copulation, shown somewhat dia- 

 grammatically. During copulation, the ventral surfaces of the two worms are in 

 contact, with the anterior ends pointing in opposite directions. A sHmy tube se- 

 creted by the clitellum of each animal surrounds the two worms, and a pair of 

 temporary seminal channels is formed on the ventral surface of each worm, so 

 that sperm expelled from the vasa deferentia of one worm travel to the openings 

 of the seminal receptacles of the other, within which they are stored. (From 

 Parker and Clarke: An Introduction to Animal Biology, The C. V. Mosby Co.) 



