ANATOMY, HISTOLOGY, AND AFFINITIES OF PHREORYCTES. 637 



The difference in the number of the spermathecse may well be only of specific value, 

 although such a difference is not usual among the aquatic Oligochseta. 



These facts, coupled with the division of the prostomium by a transverse furrow, 

 which is not found in any other Oligochseta that I am aware of, though it appears to be 

 met with in the Oapitellidse, and the complicated structure of the longitudinal muscle 

 bundles (cf. Plate, fig. 12, with Timm [pi. x. fig. 12]), lead me to regard the generic 

 identity of the present species with Phreoryctes Menkeanus as established beyond any 

 reasonable doubt. 



The salient facts in the anatomy of the genus Phreoryctes are then the following : — 



1. The body is extremely elongated, sometimes reaching a foot in length, while the 

 diameter is very small. 



2. The prostomium is divided into two by a transverse furrow. 



3. The setae, are simple, not bifid; they are disposed in four rows of single setse, or of 

 pairs of setse. 



# 4. There are no genital or penial setce. 



# 5. The clitellum occupies 3 to 4 segments from the Xth to the XHIth ; its epidermis is 

 formed by a single layer of glandular cells, differing from the epidermis of the general 

 body-surface by their glandular character and greater length. 

 6. The structure of the longitudinal muscles (Plate, fig. 12). 



# 7. The nephridia commence in the sexually mature worm in the XVIth segment. 



8. There are two pairs of testes in the Xth and Xlth segments. 



9. Two pairs of vasa deferentia opening in to the exterior upon the Xlth and Xllth 

 segments in front of the ventral setse, and opening by wide, simple (not plicated) funnels 

 into the Xth and Xlth segments. 



10. Two pairs of ovaries in segments XII. and XIII. 



11. Two pairs of oviducts opening into the exterior on segments XIII. and XIV. 

 near to the lower line between these segments, and the one in front on a line with the 

 ventral setse. The oviducts open by wide simple funnels into the interior of segments 

 XII. and XIII. The structure of these organs is exactly that of the vasa deferentia. 



# 12. Both series of ducts have the distal region lined with a chitinous membrane 

 indicating (?) their origin from an ectodermic invagination. 



# 13. The developing spermatozoa are contained in sperm-sacs, which occupy 

 segments 9 to 14 (about). 



# 14. The ova, which are when adult of very large size, undergo their development 

 in egg-sacs, which occupy segments 14 to 16 (about). 



15. The spermathecse are present to the number of from two to three pairs in 

 segments VII. , VIII. (and IX.). 



These characters distinguish the genus from any that is known, and quite justify its 

 place as the type of a distinct family, to which position it is assigned by Claus and 

 Vejdovsky [A 11]. Its relation to other families of Oligochseta are not, however, so clear. 



* The asterisks signify that the statements to which they are appended are made for the first time in the present paper. 

 VOL. XXXV. PART II. (NO. 16). 5 K 



