234 V. G. HEATHCOTE. 



The above is a short account of the early literature of 

 Chilognath development in the first stages of development, and 

 as with the exception of Metschnikoff's paper the only bearing 

 they have on my own work is to show that Chilognatha, even 

 in very closely allied species, are hatched at different stages 

 of development, I shall not refer to them again, with the 

 exception of Metschnikoff's paper, which I shall mention 

 further in the next section of my paper when discussing the 

 bearing of my own work. 



Summary. 



With regard to the segmentation I have described, it will be 

 seen that it differs considerably from that seen by Metschni- 

 koff (9), who describes it as total; the ovum being divided 

 into two, four, fee, segments. I saw nothing of such a divi- 

 sion, nor does Newport, who observed the eggs of the same 

 species as I did, record any such appearances. Newport's 

 observations were made on the eggs of a species found in 

 Madeira; that is in a hot climate; and as regards segmen- 

 tation were not carried on by means of sections. As the 

 amount and distribution of the food-yolk has a great influence 

 on the segmentation, I think it probable that in my species 

 the segmentation differs slightly from that in the species 

 investigated by Metschnikoff. The difference, however, con- 

 sisting in the external segmentation of the ovum is not, I 

 think, a very important one. The segmentation of Jul us 

 terrestris, as I have described it, shows a remarkable re- 

 semblance to that found in Amphipods by Ulianin (14). He 

 describes an external segmentation by means of shallow 

 furrows formed in the surface of the ovum, which is composed 

 in great part of food-yolk ; in each space thus marked out, a 

 large amoeba-like mass of protoplasm provided with a nucleus 

 is present ; the division of these protoplasmic masses coincides 

 with the formation of the furrows. When the blastoderm is 

 just about to be formed the furrows disappear. At the close 

 of segmentation, then the ovum is exactly like the ovum of 



