390 THE ZOOLOGIST. 



towards the posterior end, except in the bisetose species, so that 

 a form which has six setae per set in front of the girdle may have 

 four, three, or two in the tail. The set ae are shorter in the 

 middle of each bundle than at the outside. The girdle is on 

 segment twelve, the spermathecae are in the fifth segment, and 

 often possess diverticula. There are salivary glands behind the 

 pharynx, and the brain is almost invariably convex behind. 

 The microscope is absolutely necessary for determining the 

 species. 



1. Fridericia michaelseni, Bret. 



This worm was first described in 1899 by Bretscher (1) from 

 specimens found in Switzerland. Michaelsen (2) the following 

 year included it in his Oligochaeta but added no further reference. 

 Ditlevsen (3) recorded it in 1904 for Denmark, and I have made 

 many allusions to its occurrence in this country. It is one of 

 the most widely distributed species. F. michaelseni frequently 

 reaches § inch in length and is stout and active. The setae 

 usually number six in front, decreasing behind to four, three, 

 or even two. The spermathecae have a duct which usually 

 exceeds the diameter of the body in length, and there are three 

 or four round diverticula. In the Swiss examples a large gland 

 was found at the external opening of this organ, but Ditlevsen 

 failed to find it in the Danish as Southern did in the Irish forms. 

 In England there is great variation in this respect; sometimes 

 no gland is present, at other times a gland occurs on one side of 

 the body only, while in yet other instances the large gland is 

 found attached to the opening qf each spermatheca. The German 

 forms collected by me were possessed of glands. My notes are as 

 follows : 



Length 20 mm., segments 65. Dirty yellow-brown. Setae 

 6 in front, 5-4 behind. Spermathecae with long duct, four 

 diverticula, and large gland at the opening. Large male pores 

 on the girdle, which extends over segments 12 and half 13. 

 Dorsal vessel arising very far back, about segment 24 or 25. 

 Brain one and a half times longer than broad, straight or concave 

 in front and convex behind. Sperm-funnels about three times 

 as long as broad, with a distinct but narrow collar. Fully mature 



