A SOUTH AMERICAN SPECIES OF PERIPATUS. 357 



IV. Conclusions. 



On comparing the early stages of Peripatus imthurni 

 as described above with the early stages of P. cap en sis, of 

 which we now have a very complete account by Mr. Sedgwick 

 (6), there will be seen to be an extraordinary discrepancy between 

 the two forms. 



Apart from the South American forms P. Ed wards ii and 

 P. torquatus, which resemble very closely in their anatomy 

 and development P. imthurni, there is yet one more form, 

 P. novae-zealandise, about which a little is known through the 

 researches of Moseley (4), Hutton (2), and Sedgwick (6), and 

 at the development of which Miss Sheldon, of Cambridge, is 

 now working. 



A continuous series is made by the size of the ova of these 

 three forms. 



In P. novse-zealandise the ovum measures 1'5 mm. long: 

 by 1*0 mm. across ; the ovum consists almost entirely of a mass 

 of yolk, and the segmentation is meroblastic. 



In P. capensis the ovum is smaller, measuring only 17 

 mm., and though there is no yolk and the segmentation is total, 1 

 yet the spongy nature of the ovum, which consists of a very 

 loose meshwork of protoplasm, clearly shows that the ovum has 

 in this case only recently lost its yolk, and that with the loss 

 of yolk a gradual reduction of its size is taking place. 



In P. imthurni (as also in P. torquatus and P. 

 Edwardsii, as shown by Kennel) the ovum is still smaller ; 

 Kennel gives the sizs of the ovum of P. Edwardsii as "04 mm., 

 and this is also the diameter of my youngest embryo, which I 

 believe to consist of about eight segmentation spheres ; I have 

 not met with any fully ripe ova among my sections, but I 

 imagine that the embryo does not increase much in size during 

 the early stages of segmentation. 



In these forms the segmentation, as shown above, is complete, 

 and there is no appearance of sponginess such as described by 



1 Sedgwick, on page 517 of the third part of his paper, would prefer to 

 terra the segmentation of P. capensis meroblastic. 



