93 s. GOTO. 



hut tlie mcsendiyma around the terminal portion of the vas deferens 

 has assumed a character more or less different from tliat of the other 

 parts ; and althougli it is not so distinctly separated from the remaining 

 portion as in Oiichocotijle, it still forms doubtless the morphological 

 equivalent of the penis. Physiologically, too, this portion seems to 

 deserve the name, since in Hexacotijle (PI. XLl, fig. H) numerous 

 muscul'U* filjres tidvC rise from tlie papilla on the top of which the vas 

 deferens opens, and taking mostly a direction backwards are inserted 

 into tlie dorsal wall of the body. These constitute doubtless the 

 retractor muscle. In Axinc (PI. YII, tig. 5 ; PI. VIIl, üg. 3) I have 

 not been able to demonstrate the presence of any retractor ; but the ter- 

 minal p<n'tion of the vas deferens is surrounded by a mass of connective 

 tissue which is very similar to that of the penis of Oiwhocotijle with the 

 only difference that the meshes are closer and the fibres finer, and 

 which remains wholly unsüiined by b<jrax-carmin. An exactly similar 

 tissue is present in Microcotijk veticulata (PI. Y, fig. (>), a species 

 which approaches in many respects the genus Axinc. ITad a mem- 

 brane been developed around this peculiar mass of connective tissue 

 nobody would hesitate to call it the penis; but as it is, we can not 

 give it a distinct boundary. Physiologically, however, there is little 

 doubt that this tissue acts as a true penis; for in MicrocotijJc reticulata 

 and Axinc ahcrram the internal surface of this part of the vas deferens 

 is armed with numerous chitinous s})ines (PI. \", fig. O ; PI. YII, 

 fig. G a). In the former species each spine consists of a hemispherical, 

 basal portion :ind a spinous, distal portion, and is perfectly straight ; 

 in the latter species tlie spines are simple and are slightly curved. It 

 is difficult to conceive the use of the.se spines unless the portion that 

 bears them can be evaginated. 



The chitinous copulatory organ of Microcotijlc is somewhat dif- 

 ferent from those hitherto described, and will be treated of in connec- 



