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XilL — A Contribution to the Anatomy of Sutroa. By Frank E. Beddard, M.A., 

 Prosector to the Zoological Society of London. (With a Plate.) 



(Bead 4th April 1892.) 



Our knowledge of this remarkable genus of freshwater Oligochseta is at present 

 entirely due to Dr Gustav Eisen. Within a year or two of discovering the type species, 

 Sutroa rostrata* Dr Eisen found a second species, evidently referable to the same genus, 

 which has been named Sutroa alpestrisA Examples of both of these species have been 

 most kindly forwarded to me by Dr Eisen ; and I therefore take the opportunity of 

 offering a few observations upon the structure of the genus, and upon its relations to 

 other Oligochseta, as I am able, in a few matters, to supplement Dr Eisen's papers. 



The account given by Eisen of Sutroa alpestins is evidently based upon a study of 

 the living worm ; it is therefore very full as regards the vascular system, but not quite 

 so detailed where it concerns the generative organs, which are more conveniently studied 

 by the section method. It is more especially to these organs that I desire to again 

 draw attention. 



It is, however, perfectly clear from Eisen's description that the genus is correctly 

 referred to the family Lumbriculidse. The contractile vascular cseca are alone sufficient 

 to show this. So far as we know at present, no other family of Oligochseta possesses 

 these peculiar appendages of the dorsal vessel. The reproductive organs also conform 

 generally to the type met with in that family, although there are some differences in 

 detail from the remaining genera of the family. 



One rather important point in the external structure of the worm is not mentioned 

 by Eisen : I refer to the clitellum. Several of the specimens kindly sent to me by my 

 distinguished colleague were sexually mature, and in these the clitellum was fully 

 developed. I found, it to extend over nine segments, beginning with the Vllth, and 

 ending with the X Vth. In longitudinal sections it was not easy to fix with accuracy the 

 commencement and ending of the clitellum ; it did not either commence or end abruptly. 

 As in all other aquatic Oligochseta, the clitellum consisted of a single layer of cells only. 

 Those upon the clitellum differed from those upon other parts of the body by being more 

 granular and by their greater depth. 



The clitellar cells were perhaps twice the depth of the epidermic cells elsewhere ; 

 looking at a portion of the clitellum near to the middle, and comparing it with a 

 fragment of epidermis from, say, the second segment of the body, it was quite impossible 

 to confuse the characters of the epidermis of the two regions ; but the ordinary epidermis 



* On the Anatomy of Sutroa rostrata, a new Annelid of the family Lumbriculina, Mem. Calif. Acad. Sci., vol. 2, No. 1. 

 t Anatomical Notes on Sutroa alpestris, a new Lumbriculide Oligocheete from Sierra Nevada, California, Zoe, vol. 

 ii. No. 4. 



VOL. XXXVII. PART I. (NO. 13). 2 G 



