Miscellaneous. 353 



composed of a single row of papillae ; in the species from the Cape 

 they exhibit a solution of contiuuity in the middle of the back and 

 usually comprise several rows of papillie. P. ThoUoni has con- 

 tinuous Avriukles like those of the American species, but it exhibits 

 in each wrinkle one or two rows of little accessory papillae, 



(7) Jows. — In the American species the two blades of each jaw are 

 provided with an accessory tooth on the inner margin of the pi-in- 

 cipal tooth ; moreover, the inner maxillary blade is armed with a 

 long row of denticles. In the species from the Cape the accessory 

 tooth disappears on the inner blade, and the denticles of this blade 

 are much less numerous ; the same applies to the Oceanian forms, 

 but here the accessory tooth disappears on the outer blade also. 

 In P. ThoUoni the jaws are of the same type as those of the American 

 species. 



It results from the foregoing that P. ThoUoni constitutes the 

 transition between the American species of Peripatvs and those of 

 South Africa, More closely related to the former, it must be 

 regarded as having originated from the American species of Peri- 

 patus, which gradually spread towards the East at an epoch at 

 which a continental barrier still united the Xew World to the Old, 

 In proportion as this eastward dispersion of Peripalus came to pass, 

 the evolution of these animals accentuated itself in a determined 

 direction : the limbs atrophied in succession posteriorly, and, at the 

 same time, their number became more and more constant ; the 

 proximal spiiiulous arches followed, up to a certain point, the same 

 regressive course ; the nephridial papillae of two pairs of limbs 

 advanced by degrees towards the following arch ; the wrinkles in 

 the skin became more complicated, then interrupted on the dorsal 

 median line ; lastly, the dentiform armature of the jaws underwent 

 successive reduction. 



Since, in many respects, the species belonging to Oceania mark the 

 present limit of the evolution of the Onychophora, it would be possible 

 to believe that the species of Peripatus of this region are derived from 

 African species which had emigrated eastwards in geological times. 

 Eut since certain characters of these animals are somewhat primi- 

 tive (position of the sexual orifice and of the nephridial pores of 

 the fourth and fifth limbs), we may also suppose that the dispersal 

 of the gi-oup took place in both directions at the same time — towards 

 the east in the case of Africa and towards the west as regards 

 Australia and the adjacent regions. The study of the Chilian Peri- 

 patus will perhaps enable us to solve this problem. 



In any case, it appears to be quite certain that Central America 

 and the Caribbean Eegion have been the centre of origin and migra- 

 tion of the species of Peripatus ; their dispersion towards the East 

 is likewise scarcely open to doubt, and we must expect to discover 

 them in all the tropical portions of West Africa, at least as far as 

 the region of the Cape Verd Islands. — CompAes Bendus, t. (xxvi. 

 No. 19 (May 9, 1898), pp. 135S-1361. 



