THE EARTHWORM 297 



The male system (Fig. 143 D) consists of two pairs of testes 

 located in segments ten and eleven, in which they are attached to 

 the septa in the same relative position as the ovaries in segment 

 thirteen. Posterior to each testis, in a position comparable with 

 that of the funnels of the oviducts, are the s-perm funnels 

 at the inner ends of the male ducts. These are openings of rela- 

 tively large size, having crumpled walls as though one took a 

 funnel of filter paper and pleated its edges into many folds. From 

 each funnel a single vas efferens leads diagonally outward to the 

 vas deferens, which opens externally on the fifteenth segment. The 

 arrangement of the testes and their ducts, therefore, somewhat 

 resembles that of the ovaries and oviducts. The male system is 

 further complicated by the development of large seminal vesicles in 

 which the spermatozoa that have been detached from the testes 

 in an immature condition complete their development. These 

 seminal vesicles originate as three pairs of lobular bodies attached 

 to the three septa between segments nine to twelve. As they 

 increase in size the two anterior pairs become united in such a 

 manner that the region of the coelome immediately surrounding 

 the anterior pair of testes and their funnels becomes enclosed 

 as a cavity which is extended outward into the lobes of these 

 seminal vesicles. A similar relationship to the posterior pair of 

 testes and their sperm funnels develops with respect to the third 

 pair of seminal vesicles. Hence, when the immature spermatozoa 

 become detached from the testes, they are not free in the coelome, 

 but are confined to the cavities within the seminal vesicles. 

 Instead of passing immediately into the funnels, they pass into 

 these cavities of the vesicles, where they complete their develop- 

 ment before entering the funnels (Fig. 143 E to H). 



Nervous System. — The brain of the earthworm consists of a 

 pair of cerebral ganglia that are fused together and located on the 

 dorsal side of the pharjmx in the third segment (Fig. 137 C). From 

 these gangUa, the circum-'phanjngeal connedives extend around the 

 pharynx and unite to form the ventral cord, which extends to the 

 posterior end of the body. The nerves arise in pairs from this 

 central system (Fig. 143 D). There is some complexity in the 

 region of the cerebral gangha and circum-pharyngeal connectives, 

 from which the sensitive anterior region of the body is innervated, 

 but throughout the ventral region there are uniformly three pairs 

 of nerves to each segment. Hence, the nervous system of each 



