84 



LECTURE V. 



38 



duct, which, advancing forwards, unite in a common vas deferens, 

 terminating in a small vesicle at the base of the penis, which is pro- 

 vided with its pi-oper bursa. The ovaria {f,f) are two in number, 

 of a milk-white colour, situated at the margins of the middle thiixl of 

 the body, exterior to the alimentary tube. They present a dendritic 

 form, small branches being given off chiefly from their outer side. 

 The oviducts run transversely to the middle line, and form there, by 

 their convolutions, a fourth white opake body behind the testes. 

 From this subspherical body the common uterine tube (g) is continued. 

 This is a simple and ample canal, very long and tortuous, occupying 

 all the posterior part of the interspace of the alimentaj*y foi'ks, thence 

 continued forwards with decreasing convolutions, and terminating 

 at the vulva. 



The digestive system in the species of Diplostonia, a genus which 

 has two ventral suckers {Jjg. 38, b, c), is as simple as in the Dist. 



lanceolattwi ; but the blind extre- 

 mities {/,/,) of the two divisions of 

 the alimentary cavity (e, e) are each 

 lodged in a sac, i, which, from the 

 milky chaivacter of its contents, has 

 been termed the chyle-receptacle. 

 It is supposed that the nutritious 

 contents of the alimentary tubes 

 exude through the parietes of their 

 coecal extremities into these recep- 

 tacles. Two delicate vessels, k, k, 

 are continued from the anterior and 

 outer angle of each chyle-receptacle, 

 which extend forwards to the ante- 

 rior third of the body, and are there 

 brought into communication by a 

 transverse vessel, /, which extends 

 across the dorsal aspect of the body. 

 From the point of union of the 

 transverse with the external lateral 

 vessels, a single trunk is continued 

 forwards on each side to the anterior 

 angles of the body, m, m, where they 

 bend inwards and unite in the middle line to form a median 

 trunk, n, n, which is continued to the posterior extremity of the body, 

 distributing or receiving branches on each side throughout its 

 entii'e length, and apparently terminating at the posterior excretory 

 pore, h. Through the connections of this system of vessels with the 

 chyle-receptacles, the terminal pore might be regarded as an anal 



