CH. l] RANGE OF PERIPATUS. 17 



like those that occur among the segmented worms. On 

 the other hand it has the tracheae of the tracheate 

 division of the Arthropods, and at least rudimentary 

 appendages of the Arthropod type. The genus has been 

 recently the subject of a careful monograph, so that we 

 are in possession of the facts of structure and distribution 

 of a good many species. Mr Sedgwick allows eleven 

 species as well founded, and there may be others. The 

 genus occurs in South Africa, South America and the 

 West Indies, in New Zealand and in Australia; one 

 specimen is found in Sumatra ; otherwise it is absent from 

 the Oriental region. The species of the genus are mainly 

 distinguished from each other by the position of the 

 generative aperture, by the number and structure of the 

 legs and by colour. Mr Sedgwick divides them into four 

 groups which correspond to their range ; the Australasian 

 species, for instance, form one group, the neotropical 

 another, and so forth. These four main groups are largely 

 separable on account of the varying position of the 

 generative pore, which may be between the last or the 

 penultimate pair of limbs or altogether at the end of the 

 body. There are differences too in the structure of the 

 generative organs, and the eggs show characteristic 

 variations; thus, in the Australasian species the ova are 

 large and full of yolk, in the Cape species though the ova 

 are large the yolk is not abundant, and finally in the 

 neotropical species of Peripatus the ova are quite minute, 

 and without food yolk. The single known species from 

 the Oriental region is more imperfectly known than many 

 of the others ; but it seems to resemble the neotropical 



B. z. 2 



