278 



THE ANIMAL KINGDOM 



Seminal vesicle-S 



Nepliridiurrr' FunneP 

 Sperm ducV 



Ovary 

 Oviduct 



Sperm receptacles 

 Spe-rm reservoirs 



Figure 15.7. Lateral view of Lumbricus (see Fig. 15.6) with many of the viscera re- 

 moved. Reproductive and excretory systems are shown. The testes lie inside the sperm 

 reservoirs. Compare with Figure 15.4 for the external openings. 



serving not only as better oars but as better gills for increased activity. 

 After the body wall ruptures and the gametes are shed, the worms settle 

 to the bottom again and recover their former morphology and habits. 



Reproduction in Lumbricus is considerably more complex (Figs. 

 15.4 and 15.7). Segments 10 and 11 each contain a pair of testes in 

 isolated median cavities of the coelom, the sperm reservoirs. These two 

 reservoirs have three pairs of prominent lateral pouches, the seminal 

 vesicles, that extend into the 9th, 10th and 11th segments. Sperm elab- 

 orated in the testes are shed into the reservoirs and vesicles where they 

 are stored in large numbers. From the reservoirs two pairs of sperm 

 funnels collect sperm and pass them posteriorly through a pair of sperm 

 ducts to the male pores on the ventral side of the 1 5th segment. 



The single pair of minute ovaries are in the 13th segment, where 

 eggs are shed into the coelomic cavity. At oviposition the eggs are col- 

 lected by a pair of egg funnels and passed through short oviducts to 

 the ventral female pores on the 14th segment. Two pairs of seminal 

 receptacles in the 9th and 10th segments open laterally at the posterior 

 septa. Sperm received during copulation are stored here. 



The female system also includes a clitellum, a swollen glandular 

 region of the epidermis (segments 32-37). During copulation two worms 

 facing in opposite directions press their ventral surfaces together so that 

 the clitellum of one is opposite segment 10 of the other (Fig. 15.8). The 

 chaetae of one may pierce the body wall of the other, and they are also 

 glued together by thick mucous secretions of the clitellum and skin. 

 These secretions form grooves between the worms so that sperm extruded 

 on the 15th segment pass posteriorly along the mucus to the clitellum 

 where they enter the seminal receptacles of the other worm. 



Soon after copulation the clitellum secretes a membranous cocoon 

 and beneath this an albuminous secretion. The worm may then lay 

 several eggs that pass back into the cocoon, or the cocoon may slip for- 

 ward along the body so that the eggs are laid directly into it as it passes. 

 The cocoon is then moved forward and the eggs are fertilized as they 

 pass the sperm receptacles. Finally the cocoon is slipped off the head, 



