EXCRETORY AND REPRODUCTIVE SYSTEMS 29 



2. The oesopliagus is a very short straight thin-walled tube 



behind the pharynx. 



3. The intestine, into which the oesophagus opens just in 



front of the genital aperture, divides immediately 

 into a right and a left limb, each of which runs 

 to the hinder end of the body, giving off numerous 

 small caeca on its ianer side, and many large 

 branched ones on its outer side ; the whole intestine 

 forming a series of csecal tubes ramifying all over 

 the body without anastomoses. 



0. The Excretory System. 



This is almost if not quite invisible except in injected 

 specimens. It consists of a network of small much-branched 

 ducts, which commence with ciliated funnel-like mouthS' 

 opening into the lacunar spaces representiag the body-cavity. 

 These smaU ducts freely anastomose with one another, and 

 open into larger transverse ducts, which in turn open into 

 the main duct. 



The main duct is a median tube of considerable size, 

 formed by the union of four anterior ducts, a dorsal and a 

 ventral on each side, at about a quarter of the animal's length 

 from the anterior end : from this point the main duct runs 

 directly backwards to open to the exterior by a terminal 

 median pore. 



D. The Beproductive System. 



This is compHcated, as in most hermaphrodite animals. 



1. The male organs. 



a. The testes are much branched, and lie in the 



middle part of the body, extending over about 

 half its length and half its width. The two 

 testes are about equal in extent, one lying behind 

 the other. 



b. The vasa deferentia are two in number, one arising 



near the middle of each testis. They run for- 

 wards as far as the ventral sucker, where they 

 open into the vesicula seminalis. 



