THE ANATOMY. SPERM-DUCTS 99 



a recurved margin. In the Enchytraeidae it has a very peculiar form ; it is here 

 barrel-shaped, with a lining of very thick glandular-looking cells, which encroach 

 upon the lumen, reducing it to the smallest dimensions. 



Among earthworms the funnel is for the most part folded at the margins, whence 

 the term 'ciliated rosette' which is often applied to it. The folding is often 

 extremely complex. 



As a general rule the funnel of the sperm-duct opens directly into the general 

 body cavity of the segment ; sometimes, as in Lumbricus. &c., the funnels are 

 lodged in special sacs — shut off from the rest of the coelom — which contain the 

 testes, and are in communication with the sperm-sacs. The funnels commonly lie 

 close to the posterior septum of their segment, facing forwards and opposite to the 

 testes which usually are attached to the anterior septum of the same segment ; 

 a curious exception to this rule is seen in the Eudrilid genera Teleudrilus, Hyperio- 

 drilus, and Heliodrilus — perhaps also in some others. In these genera the funnels 

 depend from the anterior septum of their segment, and accordingly (see woodcut, 

 fig. 36) the vas deferens perforates this particular septum twice on its way to the ex- 

 ternal pore. In the Lumbriculidae something of the same kind occurs, owing to the fact 

 that the male genital pore lies in front of though in the same segment as the posterior 

 funnels ; these funnels face forwards and depend from the posterior septum of their 

 segment as in the majority of the Oligochaeta ; the vas deferens passes backwards 

 perforating this septum and then again perforates it on its way to the external orifice. 

 The number of funnels appears nearly always to correspond to the number of the testes ; 

 if there is only a single pair of testes there is onlj' a single pair of funnels and sperm- 

 ducts; if there are two pairs of testes the number of funnels is^ also doubled. The 

 position of the funnels is also in correspondence with that of the testes, that is to 

 say as to the number of the segment which they occupy. Very rarely this is not 

 the case. For example in Heliodrilus the testes lie a segment in front of the funnels, 

 which must necessarily occur owing to the facts already mentioned about the 

 position of the funnels. The duct ai'ising from the funne] is a tube with ciliated 

 epithelial walls ; the cells composing it are more or less quadrangular in form and 

 surround the lumen which is never intracellular. Outside the epithelium is a layer 

 of peritoneum and in a few instances, e.g. in Eudrilus, a layer of muscles between 

 the two. Very anomalous are the sperm-ducts of Fhreodrilus, where the windings 

 of the duct, which has a caecal diverticulum, are largely within the peritoneal covering ; 

 this is described more in detail below. The principal variations in the sperm-ducts 



' Not, however, apparently in many Lumbriculidae, where two pairs of funnels and one pair of testes. 



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