158 



GENERAL ZOOLOGY 



103. — Copulation i 

 foetidus. (After Foot.) 



development, they are liberated from the testes and complete 

 their development in the confines of the seminal vesicles. At the 

 proper time they escape from the seminal vesicles through the 

 four mouths of the sperm ducts (Fig. 102). 



The ovaries of the earthworm are two in number, situated one 

 on each side of the mid-line on the posterior surface of the anterior 



wall of segment 13. As the eggs 

 mature, they burst from the 

 ovaries and are conveyed to the 

 outside through a pair of oviducts, 

 each of which begins in a funnel- 

 n Hdodriius shaped opening located on the 

 posterior wall of segment 13 and 

 terminates in an opening on the outside of segment 14. 



The seminal receptacles or spermathecae are two pairs of sacs 

 in segments 9 and 10. At the reproductive period these sacs are 

 filled with sperm from another worm in the manner to be 

 described presently. Later the sperm cells are emitted to 

 fertilize the eggs. 



According to the observations of Grove on the common earth- 

 worm, Lumbricus terrestris, two 

 worms oppose each other in a 

 head-to-tail position in such a 

 manner that segments 9 to 1 1 of 

 one worm are opposite the 

 ventral surface of the clitellum 

 of the other. The clitellum is 

 an enlarged region of the body 

 composed of segments 32 to 

 37. At these points the worms become firmly bound together 

 by bands of mucus secreted by the epidermal cells which 

 soon hardens into a thin membrane (Fig. 103). There is 

 also a slighter attachment between segment 15 of one and 

 segment 26 of the other. A slime tube, composed of mucus, 

 is then secreted about each worm, save at the ventral surfaces in 

 intimate contact between segments 9 and 37. Seminal fluid 

 containing spermatozoa then issues from the openings of the 

 vasa deferentia in segment 15 and passes back through tempo- 

 rary grooves beneath the slime tube in the body wall to the clitel- 

 lum. Emission of seminal fluid takes place in each worm 



Fig. 104. — The formation of a slime 

 tube by a single worm at some period 

 after copulation, c, cocoon formed 

 about the clitellum; t, slime tube. 

 (After Foot and Strobell.) 



