526 RICHARD EVANS. 



in the male (9). This goes far to prove that the genus 

 Peripatus is more primitive than the genns Peripatopsis, 

 and that the ancestral form possessed two somites behind the 

 genital one. This view assumes the position of the genital 

 orifice to remain constant, that is, between the originally 

 penultimate pair of legs — an assumption which is sup- 

 ported by embryology and anatomy. Taking the condition 

 of the last two pairs of legs as the basis of our classification, 

 the Peripatidae fall into four groups, the first of which 

 contains three genera which show only a slight diminution 

 in size of the last pair of legs; in the second there are two 

 genera in which the last pnir has disappeared, but the last 

 but one is still well developed; in the third there is only one 

 genus, in which the second pair of legs is very much reduced ; 

 and in the fourth there is one genus in which there are no 

 signs whatever of the originally penultimate pair, the genital 

 pore being situated behind the last existing pair of legs, 

 which is reduced in size. 



In a group so small and so widely distributed it would 

 hardly be expected that one genus could be derived from 

 another. The consequence is that any kind of branching 

 arrangement intended to show their phylogenic relations 

 seems impossible, for in one genus one primitive character 

 has been retained while in nnother genus another such 

 character is found, and comparison of the several features of 

 the genera lead to the most divergent results. Hence the 

 gradation which can be traced among the several genera of 

 the Onychophora only represents steps which have been 

 reached by each genus more or less independently. If these 

 gradations be considered, as has already been done in the 

 case of the male accessory glands, the male ducts aud 

 spermatophores, the ovum, and finally the genital orifice 

 and the last two pairs of legs, we arrive at a different result 

 in almost every case — a fact which justifies the statement that 

 no branching arrangement can possibly represent the phylo- 

 genetic relations of the different genera, which appear to 

 have developed more or less independently from a common 



