SPECIES OF THE GENUS AULODRILUS. 967 



connection with the setal sacs, and in the absence of the paratrium 

 this genus resembles Tuhifex and Psammorcytes. But it differs 

 from these genera in the following important points : — 



(1) Position of the zone of formation of new segments some 

 distance in front of the anus. 



(2) Presence of a spermiducal chamber. 



(3) Presence of a muscular or coelomic sac. 



(4) Variable position of genital organs. 



(5) Absence of spermatophores and a true penis. 



(6) Absence of sapra-intestinal and parietal vessels. 



In possessing hair setfe, an anterior atrium and a coelomic sac, 

 and in having no spermatophores, it bears a remarkable resem- 

 blance to Branchiura and Kaioamuria, the chief differences being 

 the absence of a pai-atrium, the presence of penial setse and a 

 spermiducal chamber, and the absence of a true penis, which is 

 said to be present in Katoaumtria. 



Aulodrilus resembles Monopylepliorus africanus Michaelsen, 

 in possessing a spermiducal chamber, penial settB, and sperma- 

 thecse in the 9th segment, and in the absence of spermatophores 

 and a paratrium. 



The spermiducal chamber perhaps acts as a sucker during 

 copulation. As this structure is present in Monopylephorus, 

 which is however, in other respects very different from the present 

 genus, I think this organ is correlated with the absence of a true 

 penis and therefore probably is due to convergence in these 

 genera. 



(6) Summary. 



(1) The diagnostic characters of the genus and the species are 

 given . 



(2) The reproductive organs hitherto unknown are described 

 in detail. 



(3) The prostate is large and massive ; it opens into the atrium 

 near the antero- ventral margin. The prostate cells soon after 

 they are functional and filled with secretion lose their structure 

 and become disorganized, while the secretion passes as an inwaixlly 

 moviug mass into the atrium at the point where the gland is 

 connected with it. The atrial epithelium also at this time under- 

 goes a great change on account of the secretion by which its cells 

 become replaced having lost their entity. The manner of con- 

 nection of the prostate with the atrium suggests its origin as an 

 outgrowth of the atrial epithelium. 



(4) The coelomic cavity in the segment which contains the 

 spermathecge is separated off from the peripheral portion by the 

 formation of a ventro-lateral wall, which is composed of a central 

 muscular layer surrounded on either side by a peculiar parenchy- 

 matous tissue of peritoneal origin. The central chamber thus 

 formed contains all the organs of the segment and is also filled 

 with the developing spenns; the spermathecal ducts pass through 

 the ventro-lateral corners of the wall on their way to the exterior. 



65* 



