Phylum Annelida and Other Wormlike Coelomates 459 



passes through the septum, coils considerably, and then passes to the 

 outside through the nephridiopore. Thus each nephridium occupies 

 portions of two segments. Waste materials are swept by the cilia of 

 the nephridium from the coelom. Blood vessels which are closely asso- 

 ciated with the nephridium also appear to discharge waste materials. 



Dorsal to the pharynx in somite 3 is a pair of ganglia, the supra- 

 pharyngeal ganglia. This constitutes the so-called brain of the earth- 

 worm. From these ganglia, a pair of small nerves go forward and supply 

 the prostomium. Two large circmnpharyngeal connectives pass around 

 the pharynx from the suprapharyngeal ganglia to the sub pharyngeal 

 ganglia. From here, the double ventral nerve cord extends the length 

 of the body. Each segment is supplied with a ganglion on this nerve 

 cord and three pairs of lateral nerves. 



Sensory cells are present in the epidermis, particularly in the an- 

 terior portion. Many of these are sensitive to light, touch, and chemicals. 



L. terrestris is a monoecious animal. Two pairs of very small testes 

 are present in somites 10 and 11. Just posterior to each testis is a 

 ciliated sperm, funnel which passes into a very short vas efferens. On 

 each side, the vas efferens join in segment 12 to form a vas deferens 

 which opens to the outside through the pore in segment 15. The testes 

 with their funnels are within the two pairs of seminal vesicles of seg- 

 ments 9 to 13. These latter are the large conspicuous structures which 

 surround the esophagus. The sperm cells are immature when discharged 

 from the testes and complete their development in the seminal vesicles. 



The paired ovaries are in an anterior position in segment 13. At 

 the posterior portion of this same segment are the ovarian fminels which 

 pick up the ova as they are discharged into the coelom. These connect 

 to the oviducts which open to the outside on segment 14. In segments 

 9 and 10 are two pairs of seminal receptacles where sperm is stored until 

 the eggs are ready to be fertilized. 



Mating Behavior of L. terrestris.— Even though male and female 

 organs are present in each worm, self-fertilization is not possible. Copu- 

 lation between two worms occurs most frequently during warm moist 

 weather and always at night. The worms come out of their burrows, 

 stretch out with the heads pointing in opposite directions and bring their 

 ventral surfaces together. Special setae which actually penetrate the 

 body wall and sticky secretions from the clitellum and other body glands 

 aid in keeping the worms together during copulation. The clitellum of 

 each worm is opposite segments 7 to 12 of the other worm and is held 



