276 



GENERAL BIOLOGY 



closed by large white sacs, the seminal vesicles lying in somites nine to 

 twelve. There are three pairs of these sperm sacs, one in somite nine, 

 one in somite eleven, and the third in somite twelve. In somites ten 

 and eleven there are central reservoirs. 



The testes are rather difficult 

 to find in a mature worm because 

 they are quite small and the dor- 

 sal wall of the vesicle must first 

 be removed. 



The sperm are developed in 

 the testes and stored in the sem- 

 inal vesicles from which they are, 

 during the period of copulation, 

 injected into the seminal recep- 

 tacles of another worm. Fertili- 

 zation actually taking place out- 

 side the body, however. 



When the earthworm is sex- 

 ually mature there is a clitellum 



Fig. 170. Lumbncus Herculeua. Of Cmgulum ' formed, COVCring 



firstlweViZ somHes, SfSn wnen^tt Inimal SOme six Or Seven Segments. This 



L^%&l^^^t^S^^S&^ is a thickened portion often sup- 

 septa. The pins are placed in the 3rd, 9ih, and posed to be a SCar formed by the 

 18th somites. B. View ot the first sixteen somites . . * 

 of the same worm after removal of the alimen- worm after having been injured 

 tary tract, to show the nervous system and re- . _ .. . t 

 productive organs, be, buccal cavity, cut across; Or CUt in tWO. Mating may take 

 eg, cerebral ganglia ; g, gizzard ; int, intestine ; < f , i 



nph, nephridia; od, oviduct; oe, oesophagus; ov, place at any season of the year, 



ovary in somite 13; ph, pharynx with radiating i f r>mnrc tnrrA ^r^nn^ntKr in 



muscular strands; prv, proventriculus ; s, septa; DUt OCCUrS more IrcqUCntly in 



sd, sperm duct; sf, seminal funnels; spth, sper- -warm rlamn i/upatVipr 



mathecae in somites 9 and 10; sp.s, sperm sacs; Wdl - ner< 



t, testis. (After Bourne). Again quoting Latter. i Two 



worms from adjacent burrows, "each retaining a firm hold in its own 

 burrow by means of the flattened tail, apply their ventral surfaces to 

 one another so as to overlap for about a third of the length of the body. 

 The head of each worm points toward the tail of the other. The clitel- 

 lum of each secretes a band of mucus which binds the two worms firmly 

 together, so firmly, indeed, as to cause two well-marked constrictions, 

 while a slimy covering, the slime tube, surrounds the two worms from 

 the 8th to the 33rd segments. The seminal fluid, containing spermatozoa 

 ( ) and spermatophores ( ), 



flows within the slime-tube, and during sexual union, in the early stages 

 of the formation of the cocoons spermatophores cover the dorsal and 

 lateral surfaces of segments 9, 10, and 11 of each worm and are packed 

 between the two worms. The spermatozoa flow backwards from the 

 male aperture in a longitudinal groove on each side to the receptacula 

 (spermathecae) of the other worm, the grooves of the two animals to- 

 gether forming a temporary tube. Hence only one worm can emit sper- 



