ZooL.— Vol. II.] EISEN—OLIGOCHMTA. 223 



have remained, and in some species — D. Tozvnsendi and 

 D. Damonis — an increase in the number of prostates has 

 taken place. 



It is superfluous to state that the author fully agrees with 

 Dr. Michaelsen's theory of the derivation of Dichogaster 

 from ancestral Benhamias; also in the derivation of Crypto- 

 drilini from Acanthodrilide ancestors. It is impossible with 

 our present knowledge of the structure of the various spe- 

 cies of Dichogaster and Benhamia to keep the families sep- 

 arate as proposed by Beddard. 



It may be of some interest to recapitulate and review the 

 similarities between the genera Beiihatnia and Dichogaster. 

 These similarities are so many and so important that they 

 can not possibly be accounted for by chance. The follow- 

 ing characters are found in some of the species of both 

 genera: — 



1. A pellucid zone of sense-cells in the pharyngeal 

 region. 



2. A zone of sense-cells in the equator of each somite. 



3. Micronephridia covered with a coelomic mantle. 



4. A great variation in the nephridia in the different 

 species. 



5. Intestinal posterior coeca (Millsonia and Benhamia 

 ccectfera). 



6. A very characteristic arrangement and structure of 

 calciferous diverticles in XV, XVI and XVII. 



7. The form of the spermathecse. 



8. A depressed genital zone, below the general surface 

 of the body, 



9. Two forward gizzards. 



10. A tendency to variation in the position of the sperm- 

 iducal pore. 



In the following, Dr. Michaelsen's view as to the limits of 

 the genus has been accepted to the extent of placing in it 

 the genus Millsonia; but in addition, in concurrence with 

 the suggestion of Beddard, the genus Microdriltis has also 

 been included. This I know will clash with Dr. Michael- 

 sen's view as to the reduction of the prostates and their 



