DEVELOPMENT OF PER1PATUS NOV^E-ZEALANDIiE. 223 



yolk, however, differs in that he considers each yolk-segment 

 as a single cell, whereas in P. novse-zealandise I find no 

 relation existing between the yolk and the nuclei, it being 

 quite a matter of chance whether or not a yolk-segment 

 possesses a nucleus. Moreover, I do not think it necessary to 

 suppose any free nuclear or cell formation to exist in the 

 formation of the blastoderm, as there seems to be no reason 

 why all the nuclei forming it should not be derived by division 

 of the original segmentation nucleus. As to the nuclei which 

 appear in the central part of the yolk, it is more difficult to 

 account for them as originating from any pre-existing nucleus, 

 as they are very far removed from any one, and the three 

 chromatin particles in a mass of protoplasm, which are figured 

 in fig. 10, rather point to the formation of nuclei by a pro- 

 cess of aggregation of such particles. The segmentation 

 also bears a considerable resemblance to that of Peripatus 

 capensis; in fact the differences between the two may in all 

 probability be accounted for by the presence of the yolk in the 

 New Zealand species. They also resemble one another in the 

 absence of any cell outlines, the protoplasm in P. novse- 

 zealandise, as in P. capensis, forming a perfectly continuous 

 reticulum in which the nuclei are embedded ; this is very 

 especially noticeable in certain stages in the former species, as 

 is shown in fig. 12. The curious forms assumed by the nuclei 

 also resemble those found in P. capensis, although owing to 

 the difficulty presented by the yolk in cutting sections of the 

 young stages I was not able to get sections sufficiently thin to 

 enable me to examine them in detail. It is nevertheless per- 

 fectly obvious that the nuclei often present the same curious 

 phenomenon of being divided by septa into numerous compart- 

 ments. These two points, however, viz. the continuity of the 

 protoplasm and the forms of the nucleus, have been sufficiently 

 discussed by Mr. Sedgwick in his papers on P. capensis, and 

 need not be further considered here. 



The mode of development from the segmentation up to the 

 two last stages described in this paper presents many very 

 curious facts, and indeed, so far as I know, is without any 



