Dr. W. Michaelsen on the EnchytrgeidEe. 417 



angulated at the apices, which do not pass the broad basal seg- 

 ment of the abdomen. Anterior femora armed beneath with 

 two strong spines, one near base and one near apex. 



Long. excl. tegm., (^ 36 millim., exp. tegm. 115 millim. 



Hab. Andaman Islands, Port Blair [Meldola). 



LXI. — Studies on the Enchytrseidge. 

 By Dr. W. Michaelsen *. 



[Plate XVIII.] 



As regards the systematic arrangement of the family Enchy- 

 traeidee we have before us two different modes of treatment : — 

 1. Claparbde's old division into the genera Encliytrceus, 

 Henle, and Pachydrilus, Clap.f, to which the genera Ana- 

 cJiceta.y Vejdovsky, Distichopus^ Leidy, and Buchholzia^ aut., 

 were subsequently added ; and 2. The newer classification by 

 Eisen into the three genera Mesenchytrceus^ Archienchytrceu,Sj 

 and Neoenchytrceus \. 



Eisen founds his classification in the first place upon the 

 form of the cerebrum, having previously amalgamated, the 

 genera Enchytrceus and PacJiydrilus. In justification of this 

 amalgamation he says : — " It is evident, as Ratzel and others 

 have shown, that the colour of the blood is hardly a character 

 of sufficient value to permit us to found on it the distinction 

 of genera ; " and he adds, " It may also be remembered that 

 one of Clapar^de's species, PacJiydrilus lacteus, has white 

 blood, and that not all red-blooded live in water." The con- 

 clusion deduced from this statement would be justified if the 

 colour of the blood and residence in water were actually tlie 

 only points in which the Pachydrili differ from the other 

 Enchytrgeidas. But this is not the case. There are other 

 essential characters by which the red-blooded Enchytrseidge 

 are characterized as a perfectly natural group which may 



* Translated by W. S. Dallas, F.L.S., from a separate copy, for- 

 warded by the Author, of his paper entitled "Enchytr£eiden-Studien,'' 

 published in the ' Archiv fiir mibroskopische Anatomie/ Band xxx. 

 pp. 366-378 (1887). The numbers attached to the Author's notes have 

 been retained in parentheses in all cases where the titles of works 

 or memoirs are given. This will facilitate reference throughout the 

 paper. 



t (1) Claparede, 'Kech. Anat. sur les Ann^lides, Turbellaries, Opalines 

 et Gregarines ' (Geneva, 1861). 



X (2) Eisen, " On the Oligochseta collected during the Swedish Expe- 

 ditions to the Arctic Regions, in the years 1870, 1875, and 1876," in 

 Kongl. Sveusk. Vet.-Akad. Handl. Bd. xv. 1877 (Stockholm, 1877-79). 



