On the Structure of a New Species of Ecirthworm. 371 



system, I may refer to this very genus Acantliodrilus. In 

 several species the setre are in four series of pairs equidistant 

 from each other, as in Zu7nhricus ; in others the setse are 

 arranged throughout the body in eight series ; while in A. 

 capensis, as already stated, the disposition of the setae is inter- 

 mediate in character. It must be remembered, of course, that 

 all these species agree with each other in their internal struc- 

 ture so closely, that it is quite impossible to regard them as 

 belonging to different genera; and if the distribution of the 

 setae were to be regarded as an indication of specific difference 

 and resemblance, certain species oi Acantliodrilus would have 

 to be placed within the same genus as Lumhricus, and sepa- 

 rated from their immediate allies. 



I have also in this paper recorded for the first time the 

 position of the ovaries and their ducts, which have not as 

 yet been seen in any Acanthodrilus. 



Another fact of some interest from the point of view of the 

 comparative anatomy of earthworms, is the structure of the 

 body wall. The remarkable arrangement of the longitudinal 

 muscles in Lumhricus was first thoroughly made known by 

 Claparede's elaborate researches. It appears, however, that 

 this bipinnate disposition of the fibres is by no means charac- 

 teristic of earthworms as a group, and is only found here and 

 there ; indeed, up to the present the only other earthworm 

 besides Lumhricus where it has been recorded is in a species 

 of Perichceta {P. hasseltii ^) ; other species of this genus in- 

 vestigated by Perrier,^ Horst,^ and myself, do not present 

 this bipinnate disposition of the longitudinal muscular coat. 

 Acanthodrihis capensis must be placed in the same category 

 with Lumhricus and Ferichceta hasseltii. The disposition of 

 the longitudinal muscular fibres agree precisely with those of 

 the two latter species. Two other species of the genus 

 Acanthodrilus differ from A. capensis, in that the longitudinal 

 muscles form a continuous layer round the whole of the 

 body, the individual fibrils being separated into groups or 

 singly by anastomosing trabeculse of connective tissue, which 

 present no approximation to the symmetrical bipinnate 



1 Loc. cit. 2 ]srouv. Arch. d. Museum, t. vii. 



2 Notes from the Leyden Museum, vol. v., p. 185. 



VOL. VIII. 2 A 



