ANNELIDA. 



209 



municate by a common canal ; and the contained fluid, which like 



the seminal secretion of other animals contains animalcules, can 



readily be made to pass from one to another. 



The ovaria (c) are eight large ' Fig. 85. 



white masses of a granular texture, 



from which arise two delicate tubes 



or oviducts ; these have no connection 



with the testes, but, running back- 

 wards, they become dilated into two 



small vesicles at their termination 



(d), and open by two apertures or 



vulvse seen externally upon the six- 

 teenth segment of the body : in these 



'ducts eggs have been detected as large 



as pins 1 heads. 



(251.) The eggs, when laid, are two 



or three lines in length. In figure 85, 



A, one of them enclosing a mature em- 

 bryo is delineated ; its top is seen to 

 be closed by a peculiar valve-like 

 structure adapted to facilitate the 

 escape of the worm, and opening 

 (Jig. 85, B) to permit its egress. 

 Another remarkable circumstance ob- 

 servable in these eggs is, that they very generally contain double 

 yolks, and consequently two germs, so that a couple of young 

 ones is generally produced from each. 



(252.) The generative system of the Nais presents a somewhat 

 different arrangement to that which exists in the earthworm. The 

 swollen part of the body in which the sexual organs are placed, occu- 

 pies a space of five or six rings, beginning at the eleventh. On each 

 side of the eleventh segment is a minute transverse slit (Jig. 86, b) 

 communicating with a slightly flexuous canal which terminates 

 in a transparent pyriform pouch or vesicle. The latter con- 

 tains a clear fluid, in which minute vermiform bodies are seen 

 to float, and most probably represents the testis. The twelfth 

 segment likewise exhibits two openings, each placed upon the 

 centre of a little nipple (c), these are the orifices leading to 

 the female portions of the sexual system. The ovaria (</, e) 

 are composed of four large and several smaller masses of a 

 granular character, and from them proceed long and tortuous 



