The Earthworm 



277 



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 takes place outside 

 the body. 



When the earthworm is sex* 

 ually mature, a clitellum, or 

 cingulum, is formed, covering 

 some six or seven segments. This 

 is a thickened portion often sup- 

 posed to be a scar formed by the 

 worm after having been injured 

 or cut in two. Mating may take 

 place at any season of the year, 

 but occurs more frequently in 

 warm damp weather. 



Again quoting Latter : 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; 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 aperature in a longitudinal groove on each side to the receptacula 

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

 together forming a temporary tube. Hence only one worm can emit 

 spermatozoa at any given time, otherwise there would be opposing 

 currents. The worms are so placed that the ninth segment of each is 



Lumbricus Herculeus. 



A. A view of the organs contained in the 

 first twenty-two somites, as seen when the animal 

 is opened by a longitudinal dorsal incision, and 

 the body walls are pinned out without cutting the 

 septa. The pins are placed in the 3rd, 9th, and 

 18th somites. B. View of the first sixteen somites 

 of the same worm after removal of the alimen- 

 tary tract, to show the nervous system and re- 

 productive organs. be, buccal cavity, cut across; 

 eg, cerebral ganglia; g, gizzard; int, intestine; 

 nph, nephridia; od, oviduct; oe, oesophagus; ov, 

 ovary in somite 13; ph, pharynx with radiating 

 muscular strands; prv, proventriculus ; s, septa; 

 sd, sperm duct; sf, seminal funnels; spth, sper- 

 mathecae in somites 9 and 10; sp.s, sperm sacs; 

 t, testis. (After Bourne.) 



