1897.] FROM SOUTH AFRICA. 345 



setse is quite smooth ; but a little way in front of this tlie shaft 

 of the seta is encircled by a series of ridges which are perfectly 

 smooth and not denticulate in any way ; their direction is curved. 



§ General RemarTcs, 



This interesting collection of Acanthodrilus suggests several 

 observations of a general character. lii the first place, to meet 

 with the genus so very prevalently in the Cape Colony is remarkable, 

 though not perhaps altogether unexpected. That there are so 

 many species (10) seems to negative any suggestion of accidental 

 importation, as does their occurrence not only in the near neigh- 

 bourhood of Cape Town, but at such distant places as the Knysna 

 Forest. There is also the noteworthy fact that the Acanthodrili 

 of South Africa belong to a distinct group of the genus, not 

 unknown it is true elsewhere, as will be pointed out presently, but 

 embracing all the species (with the possible exception of the 

 originally described species Acanthodrilus capensis). This again is 

 not suggestive of accidental importation. It may, I think, be fairly 

 assumed that the species described in the present communication 

 are truly indigenous. This being the case, we have a fauna 

 of Earthworms in the temperate pai't of the African continent 

 which is totally imlike that of tropical regions (characterized as it 

 is by the Eudrilidse and by the Acanthodrilid Benhamia, not 

 Acanthodrilus) of that continent, and like that of South America 

 and New Zealand. We have, in fact, in the three great land- 

 masses which extend from the northern into the southern 

 hemisphere — if we may allow a former connection between 

 Australia and New Zealand — a sharp demarcation between the 

 earthworm fauna of their southern and of their equatorial regions. 

 Id all of them Acanthodrilus is the prevalent genus of the 

 Antarctic half. The bearing of this fact upon the theory of a 

 former extension northward of the existing Anctartic continent has 

 been so often referred to by me, that I need do no more than 

 allude to it. I may, however, remark that since I have written 

 upon that matter Dr. Eisen has described two species of Acantho- 

 drilus from California. But I am of opinion that this fact, like 

 the spreading northward of Microscole.r, is not fatal to my views. 



To assume the converse, that this genus has started in the north 

 and migrated southwards, is difficult^ if we keep firmly hold of 

 the fact that there is so little difference between the species of 

 Patagonia and the Cape of Good Hope, not to mention New 

 Zealand. The only alternative is to assume what is certainly 

 becoming more and more fashionable as an assumption — a two- 

 fold or three-fold origin of the worms which are here, and by all 

 other writers, placed in one genus, Acanthodrilus. If, however, 

 this view is to be entertained at all it cannot, in my opinion, be 



^ Since these words were written I have received from Dr. Michaelsen a 

 paper (" Weiterer Beitrag zur Systematik der Kegenwiirmer," Verh. Hamburg, 

 1896) in which the tropical origin oi Acanthodrilus is ably urged. 



Pkoc. Zool. Soc— 1897, No. XXIII. 23 



