STUUOTUEE OF EARTHWORM OF GENUS DIACH.ETA. 165 



sharply curved ; these setae are found on about the first 

 ten segments ; after this they still occur, being sometimes 

 (fig. 6a) of very large size, but are mingled with setse (fig. 5) 

 of the usual lumbricid pattern, and of which no special 

 description is necessary j these setse gradually come to be the 

 only only ones present, and towards the end of the body their 

 free extremities are much more hooked. Benham has re- 

 marked (5, p. 90) that inDiachseta Thomasii "the extre- 

 mity is more strongly curved than in the ordinary setse of 

 Lumbricus." 



At the tail end the setse become enormously enlarged (figs. 

 3, 4) ; they are so large that their amber-yellow colour can 

 be distinctly recognised by the unarmed eye, and their strongly 

 recurved apices catch in the skin when the worm is held by the 

 tail, and produce the impression of some sticky substance. 

 In a recent number of ' Nature ' I have referred to the pro- 

 bable use of these setae, viz. to give the worm a stronger hold 

 upon the ground when it is lying outside its burrow with only 

 the tail concealed. These large hooked setae, although all are 

 larger than the setae of the segments in the middle of the body, 

 vary much in size, as will be seen from an inspection of 

 figs. 3, 4. On the whole, they increase in size towards the 

 end of the body. The last few segments have fewer setae ; 

 their numbers in the last few segments of one individual were 

 as follows — 8, 7, 7, 7. 



Though most earthworms are furnished with two kinds of 

 setae, I am not acquainted with any case which is quite com- 

 parable to the present. It is remarkable to find that the 

 sculptured setae of the anterior segments become less nume- 

 rous upon the clitellum than they are in the segments in front 

 of it, for the reason that the similar setae of Urochaeta and 

 Rhinodrilus, two genera evidently allied to Diachaeta, 

 are either confined to or better developed upon the clitellum. 



The clitellum occupies a large number of segments, per- 

 haps as many as in D. Thomasii (5), but I am not able to 

 state the exact number. 



So much, then, for external characters, the description of 



