390 



MR. F. E BEDDARD ON THE 



[Apr. 19, 



round the middle of the body, as in other Perichcetce, are much like 

 those of other species on the hinder part of the body, that lying 

 posterior to the clitellum ; the setae of the anterio'r segments of 

 the body agree very closely in their shape with these, but are very 

 much larger. On the clitellum, however, the setae are very different 

 in appearance ; they are (woodcut, fig. .3) of very small size com- 

 pared to the setae of the anterior preclitellar segments, and ter- 

 minate in a distinctly bifid extremity ; the two points in which the 

 seta ends diverge at a considerable angle from each other, but are 

 connected by a delicate membrane. The opposite extremity of 

 the seta, which is imbedded in the body-wall, is abruptly trun- 

 cated. The whole seta has not the 8-shaped curve which is so con- 

 stant a character in the group, but is curved only in one direction. 

 As in the other setae of the same species, and in the setae of Earth- 

 worms generally, the middle part is somewhat thicker ; but this 

 region does not lie in the middle of the setae but is closely approxi- 

 mated to the posterior extremity ; the part of the seta which lies 

 behind the dilated region is straight. The general shape of these 

 clitellar setae, apart, of course, froin the bifid extremity, is like that 

 of imperfectly developed ordinary setae. That this is not really the 

 case with these setae is, however, clearly shown by the fact that all 

 the setae of the several rows comprised in the clitellum have precisely 

 tlie same shape, and also by the fact that in two specimens of the 

 worm, which were the first that came to hand, the structure of these 

 clitellar setae was precisely identical. 



This is, I believe, the first record of any such modification of the 



Clitellar seta oi Perichmta hoidleti. 



clitellar setae in the genus Perichceta. In P. affinis I have been able 

 to satisfy myself that the clitellar setae differ in no respect from the 

 setae of the general body-surface ; in P. indica setae appear to be 

 altogether wanting upon the segments of the clitellum. There are, 



however, other species of Lumbricidae in which there is a per- 

 fectly analogous modification of the setae ; in Lumbricus the clitellar 

 setae are distinguished from those upon the other segments of the 



