62 RANGE OF PEBICH.ETID.ffl. [ch. I 



of equal calibre throughout. This genus just gets into 

 the Ethiopian region where it is represented by the 

 species Perionyx zanzibarious, and possibly by another at 

 Durban. The true Perichceta is rare in Africa but 

 reappears on the opposite side of the Atlantic in Tropical 

 America and the West Indies. As there are a con- 

 siderable number of species on one side of the Atlantic 

 which are not found upon the other it seems likely that 

 the genus is indigenous in the New as in the Old 

 World. 



It is held by some that the characteristic mark of the 

 Perichaetidse, the continuous circle of setse amounting 

 often to more than one hundred in a single segment, is a 

 primitive arrangement from which the more general eight 

 setse per segment can be derived by reduction ; at present 

 however the matter is one which cannot be definitely 

 decided. If it prove ultimately to be the correct view, it 

 is noteworthy that the genus, like other ancient forms, 

 has a wide and discontinuous distribution, starting in the 

 Old World, and skipping Africa and Europe almost 

 entirely to reappear in the more tropical parts of America. 

 Moreover it is significant that in this group, as with the 

 mammals, Australia has the more ancient forms. 



The family GeoscolicidsB present some interesting 

 facts in their distribution. The family is one of the more 

 modern, on the view that I take myself of the affinities of 

 the group. The spermathecse have lost or at any rate do 

 not possess the diverticula so characteristic — practically 

 universal — in the Megascolicidae. In this they agree 

 with the European Lumbricidse — our common earthworms 



