STRUCTURE OF TWO NEW GENEEA OF EARTHWORMS. 271 



and not vice versa. There is at any rate nothing in the facts 

 which is opposed to this view, though the converse might be 

 asserted with some probability. 



As Dr. Michaelsen has pointed out, the two vasa deferentia 

 of each side retain their distinctness, but are accurately super- 

 imposed, thus giving rise to the impression that but one tube 

 is present. 



A curious peculiarity in the vasa deferentia of Eudrilus, 

 which appears to be confined to that genus and to other 

 Eudrilidse, was first pointed out by myself. In those genera 

 each vas deferens has, like the atrium into which it opens, a 

 well-developed muscular tunic ; each vas deferens, moreover, 

 in those very aberrant earthworms commences with a very 

 wide dilatation immediately connected with the funnels. 



In both these points Nemertodrilus difi'ers from its two 

 allies — the vas deferens has neither the oval or spherical di- 

 latation nor the muscular coat ; it conforms, in fact, in every 

 particular to the usual type met with among earthworms. 



Michaelsen mentions that the two vasa deferentia of each 

 side, maintaining their distinctness to the very last, become 

 lost in the body-wall just in front of the atria. 



This is undoubtedly the impression which a dissection of 

 the Annelid produces, but it is not perfectly accurate. The 

 point is one of some little importance as touching the affinities 

 of Nemertodrilus to Eudrilus. 



In the latter genus I showed that the vasa deferentia opened 

 into the atrium at about the middle of its length. In Teleu- 

 drilus Rosa has stated that the vasa deferentia also open into 

 the atrium. 



In Nemertodrilus a series of longitudinal sections shows 

 that the two vasa deferentia cross the atrium close to its ex- 

 ternal aperture ; they then traverse the muscular coat exactly 

 as in Eudrilus, and each may be recognised still preserving 

 its independence as a ciliated tube lying between the epithelial 

 lining and the muscular coat. They finally open into the 

 interior of the atrium. 



Michaelsen has pointed out two characters in which Name r- 



VOL. XXXII, PART II. — NEW SEE. 8 



