ZooL— Vol. II.] EISEN—OLIGOCHyETA. 225 



sperm-ducts in the intersegmental groove in IJ. Ribaiicourti. 

 It may further be seen that the reduction of the prostates 

 is often but not always accompanied by a corresponding 

 reduction in the anterior pair of spermathecee. In one spe- 

 cies the anterior pair of spermathecge has been reduced but 

 the prostates have been increased. 



In D. Da?nonis, for which species the genus Dichogaster 

 was created by Beddard, the only pair of spermathecse is 

 found in somite VIII and not in IX, the reduction in this 

 species having taken place in the posterior pair of sperma- 

 thecae and not in the anterior pair. Under these circum- 

 stances, the validity of the theory advocated by Dr. 

 Michaelsen, that the reduction of the posterior prostates is 

 accompanied by a reduction of the anterior spermathecae, is 

 questionable. Should we eliminate from the genus Dicho- 

 gaster any species with spermathec^ in somite VIII, then 

 we would have to drop from the genus the very species for 

 which the genus was created. 



Since the above was written, the author has received from Dr. Michaelsen his inter- 

 esting paper on Balanta (29). In this paper Ur. Michaelsen enlarges yet further upon 

 his views in regard to the reduction of the anterior spermathecae and the posterior 

 prostates. If we consider all the known species of Dicliogaster, it will be seen that the 

 theory does not hold good in all instances, and cannot, therefore, be considered of 

 universal importance. The accompanying diagram, arranged in accordance with that 

 constructed by Dr. Michaelsen, will, I think, show the variations in the reduction of the 

 prostates and spermathecje. Here it will be seen that while in Dkhof^astcr Crawi the 

 posterior prostates have been reduced, the anterior and corresponding sperniathecte 

 remain; and also that although the posterior spermathecae have been eliminated in 

 D. Damonis, the anterior prostates still remain. Moreover, the diagram shows that 

 while in some species the sperm-ducts have been moved forward, no corresponding 

 elimination of prostates and spermathecae has taken place. In order to make the 

 diagram more useful I have included the gizzards and diverticles and also endeavored 

 to show the three kinds of nephridia. The diagram of D. nigra will serve also for 

 D. minniSy D. Braunsi and D. Hnpferi. In D. mimus the sperm-sacs are in XI and XII. In 

 the other two species they are unknown. 



