208 



ANNELIDA. 



bodies in which the generative glands are situated, are observed 

 to remain for a considerable time in contact, joined to each other 

 by a quantity of frothy spume which is poured out in the neigh- 

 bourhood of the sexual organs. No organs of intromission, how- 

 ever, have ever been distinguished, neither until recently had the 

 canals communicating between the sexual orifices and the testicular 

 or ovarian masses been satisfactorily traced ; so that Sir Everard 

 Home* was induced to believe that, in the kind of intercourse 

 above alluded to, there was no transmission of impregnating fluid 

 from one animal to the other, but that the excitement produced 

 by mutual contact caused both the ovaria and testes to burst, so 

 that the ova escaping into the cells of the body became there 

 mingled with the spermatic secretion, and being thus fertilized the 

 ova were hatched internally, and the young, having been retained 

 for some time in the cells between the intestine and the skin, 

 were ultimately ejected through apertures which were supposed to 

 exist in the vicinity of the tail. There is, however, little doubt 

 that what Sir E. Home conceived to be young earthworms were 

 in reality parasitical Entozoa, and that, in the mode of their pro- 

 pagation, the animals we are describing exhibit but little deviation 

 from what we have already seen in the leech. 



(250.) According to M. Duges,-f- the arrangement of the sexual 

 parts is represented in the diagram (fig. 84). The testicles (b) are 



placed in successive segments of 

 the body from the seventh back- 

 wards ; they 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 bot- 

 tom 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- 



* Lectures on Comp. Anat. vol. iii. 



Fig. 84. 



t Ann. des Sciences Nat. vol. xv. 



