THE ANATOMY. SPERMATHECAE 



129 



Fig. 34- 



they contain, in mature worms, spermatozoa, absent in the pouches themselves (see 



accompanying woodcut, fig. 34). Acanthodrilus disifimilis may be used to illustrate 



the first point ; in this species there are two diverticula to each spermatheca ; they 



are lined with an epithelium which is largely converted into irregular masses of an 



amorphous appearance, in which are imbedded bundles of spermatozoa ; it looks very 



much as if the lining epithelium had become converted into a substance, the function 



of which was to hold firmly the spermatozoa until they were transferred to another 



individual. In other worms the diverticula are lined with 



a low quadrangular epithelium differing so far from the tall 



columnar cells which line the pouch ; this is the case with 



Perichaeta and other genera. In no case have I observed 



an absolute similarity between the epithelium of the pouch 



and of the diverticulum ; in no case have I found any 



spermatozoa in the pouch itself; they were always in the 



diverticula. ROSA has indicated an exception to this ; no 



doubt it may easily happen accidentally that the sperm 



goes astray and finds its way into the wrong cavity ; the 



very fact that ROSA thought it worth while to mention the 



exception shows how widely prevalent is the rule. It is 



very curious that the spermatozoa should choose the narrow 



path leading to the interior of the spermathecal appendix 



rather than the broad and, one would have thought, easier 



road into the spermathecal pouch. It has been suggested 



by BKNHAM that when the male apparatus is everted in 



copulation (this can at any rate take place in some worms) 



and pushed into the spermatheca, the everted portion blocks 



the route to the spermatheca, but leaves free the aperture 



of the sperm-duct which is directed into the appendix. 



The .question of the function of the various parts of the 



spermathecal apparatus will be discussed later (see below). 



Apart from the presence or absence of diverticula, the number and position of 

 the spermathecae vary in different families of the Oligochaeta. They are sometimes 

 further forward, and sometimes more posterior in situation. The most anterior 

 position in which they occur is seen in the genus Aeolosoma; here the first pair 

 of spermathecae may be as far forward as segment iii. In the Lumbriculidae and 

 in some Geoscolicidae they are as far back as they .are ever found viz. in 

 segments xiv-xvi. 



s 



LONGITUDINAL SECTION 



OF THE SPEEMATHECA 



OF A BENHAMIA. 



(After Horst.) 



i. Diverticxilum containing 

 sperm. 



