BRITISH WELL-WORMS. 3 



the earthworms they are usually in pairs. In some species the 

 perfect seta has an imperfect one by its side, and the seta of the 

 dorsal portion of the body usually vary from those of the ventral. 

 Even in the species which has the normal arrangement of the 

 setse we still find a difference in size between the dorsal and 

 ventral pairs. Several biologists have pointed out the existence 

 here, as among the Enchytraeids, of a peculiar appendage to 

 the ventral nerve cord in each segment. Normally there are 

 two pairs of testes in segments ten and eleven, and two pairs of 

 ovaries in the twelfth and thirteenth segments, as was first 

 clearly indicated by Mr. V. E. Beddard. There are two or three 

 pairs of spermathecae in the species already described. The 

 prostomium is generally divided by a constriction. Mr. Beddard 

 has described a closely related genus under the name oi Pelodrilus 

 the two genera being placed together under the Family 

 Phreoryctidae. He gives the following definition of the 

 Family : — 



" Definition. — Aquatic or terrestrial Oligochaeta of slender form, 

 often exceedingly long. SetiE in four rows of single setae or paired, 

 sigmoid. Testes in X., XI. Ovaries in XII., XIII. or XIII. only, 

 Sperm-ducts, two pairs opening separately, without spermiducal glands. 

 Spermathecae in front of testes, without diverticula. No genital setae." 



In one or two particulars this definition will now require 

 modification. In regard to the setae we shall have to read in 

 future — " Set^e in two or four rows," and some qualification of 

 the phrase about genital seta; must be introduced. Mr. Beddard 

 next proceeds to define the genus Phvcovydcs. First we have the 

 synonyms as follows : — 



Phreovyctes, Hoffmeister. 

 Haplotaxis, Hoffmeister. 

 Nemodi'ilus, Claparede. 

 Geovydes, Schlotthauber. 



According to Dr. Michaelsen, whom I shall quote later, this 

 synonymy is incomplete. 



" Definition. — Seta; in four rows of single setas or pairs. 

 Clitellum XI.— XIV. Prostomium divided by a transverse constric- 

 tion. Testes in X., XI. Ovaries in XII., XIII. Vasa deferentia open 

 separately on to XI. and XII. ; oviducts on to border line between seg- 

 ments Xll/Xill. and XIII/XIV. Spermathecas, two or three pairs in 

 VII., VIII. (IX.)." 



Here again the same modification applies to the setae. We 

 now come to a consideration of the known species. When Mr. 



