GENERATIVE SYSTEM OF THE EARTHWORM. 



235 



Fig. 114. 



vary in number in different individuals, from two to seven ; but whether 

 this variety depends upon a difference of species, or is only caused by 

 the posterior pairs becoming atrophied when not in use, is undetermined. 

 Each testis is fixed to the bottom of 

 the ring in which it is placed by a 

 short tubular pedicle that opens 

 externally by a very minute pore, 

 through which a milky fluid can be 

 squeezed. The testicular vesicles of 

 the same side of the body all com- 

 municate by a common canal ; and 

 the contained fluid, which, like the 

 seminal secretion of other animals, 

 contains spermatozoids, can readily 

 be made to pass from one to another. 



(610.) The ovaria (c) are eight 

 large white masses, of a granular 

 texture, from which arise two deli- 

 cate tubes or oviducts ; these have 

 no connexion with the testes, but, 

 running backwards, they become di- 

 lated into two small vesicles at their 

 termination (d), and open by two 

 apertures or vulvae seen externally 

 upon the sixteenth segment of the body : in these ducts, eggs have been 

 detected as large as pins' heads. 



The following is Dr. Williams's account of this mysterious appa- 

 ratus* : 



(611.) The generative system of the Earthworm is situated in the 

 immediate vicinity of a thickened ring or band, bounded by abrupt 

 limits, which implicates six or eight of the annuli of the body. This 

 thickening, when closely examined, is found to depend upon an extra- 

 ordinary development of the cutaneous follicles. On the abdominal 

 aspect of this thickened portion suctorial cups are formed, by aid of 

 which, during the congress of two individuals, mutual contact is main- 

 tained ; but the generative segments internally have no relation with 

 this suctorial ring of integument, nor has this latter part anything 

 to do with the true genitalia. It is, like the thumb of the Frog, a 

 mere provision for the mutual apposition of two individuals. The en- 

 larged follicles of this cutaneous ring, moreover, discharge another func- 

 tion they supply the peculiar glutinous secretion which affords a pro- 

 tecting capsule to the ova as they escape from the body. 



(612.) Every ring in the body of this worm (except a few at the head 

 and tail) contains two ' segment organs,' one on either side of the intes- 

 * Phil. Trans. 1858. 



Arrangement of the sexual organs in 

 an Earthworm. (After Duges.) 



