348 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



opacity are due to the presence of parasites belonging to 

 the species Urospora saenuridis, which will be described 

 later. 



The reproductive system is a complex affair, as is 

 usually the case in hermaphrodite forms, and it will be 

 well, first of all, to enumerate the various organs which 

 assist in the process of reproduction and then enter into 

 their structure and arrangement in detail afterwards. 

 First, then, there are the ovaries (PL I, fig. 2, ov.) and 

 testes in which the ova and spermatozoa respectively 

 undergo the earlier stages of their development. They 

 are not, however, permitted to come to maturity in these 

 organs, but are transferred quite soon to special sacs 

 known as the egg sacs (PL I, fig. 3, ovs.) and sperm sacs 

 (PL I, fig. 2, sp. s.), which, at first, occupy only one 

 segment each, but in the mature worm may extend through 

 several segments. When the ova and spermatozoa are 

 fully developed, they are transferred to the cocoon by 

 means of special ducts, which are provided with external 

 apertures perforating the body wall. These ducts are 

 known as the oviducts (female) and the sperm ducts or 

 vasa deferentia (male) (PL I, fig. 2, v. d.). The sperma- 

 tozoa do not reach the cocoon directly, by means of the 

 vasa deferentia, but are transferred, during copulation, 

 to special organs set apart for their reception. These 

 organs are known as the spermathecae (PL I, Rg. 2, sp.). 

 The terminal portion of each vas deferens is dilated to 

 form an elongated chamber known as the spermiducal 

 gland (PL I, fig. 2, at.), which opens to the exterior by 

 the penis, a chitinous organ, capable of protrusion 

 (PL I, fig. 2, pe.). The penis aids in the transference 

 of the sperm from the sperm sac of one worm to the 

 spermathecae of the other during copulation. In con- 

 nection with the spermiducal gland, and formed as a 



