266 ClIAS. W. HARGITT, 



and general in Crustacea and Insecta, tho not lacking in others, e. g. 

 Myriopoda and Arachnida, where similar conditions are found. 



Briefly summarized the phenomena of early development appear 

 to be somewhat as follows: Upon the maturation and fertilization of 

 the egg, as previously described, and following the apparent dissipation, 

 or perhaps fragmentation of the nucleus, its early reorganization into 

 one or more nuclear centers constitutes the initial impulse of deve- 

 lopment. With the massing of deutoplasm in the center of the egg the 

 cytoplasm, as already noticed, has been forced into a peripheral layer, 

 tho with something of a reticular network throughout the entire egg. 

 In the nuclear activity and division which now takes place the cyto- 

 plasm is but slightly involved, or at any rate no specific divisions 

 occur within its mass giving rise to independent cells^ tho cytoplasmic 

 condensations occur in close relation with each nuclear center, as 

 shown in Figs. 24 and 25. Under the stimulus of these associated 

 activities the deutoplasm within the cytoplasmic reticulum becomes 

 also involved and a definite cleavage occurs in a more or less orderly 

 fashion till the entire mass becomes divided in a series of cell-like 

 bodies, or yolk-balls, composed of the primary yolk-spheres, which are 

 of varying size and shape. Within some of these yolk-balls are found 

 resting, nuclear-like bodies, perhaps true nuclei, but in others no such 

 centers are demonstrable. The nuclear character of these is further- 

 more strongly suggested in that, as will be farther noticed later, they 

 appear to become centres of active metabolism, and indeed of nuclear 

 proliferation. 



These superficial aspects of cleavage never appear to go beyond 

 that shown in Fig. 13, including perhaps from thirty, or at most fifty 

 such cells. Internally however the case seems quite otherwise. 

 Following the yolk cleavages and perhaps including also to some 

 extent the cytoplasm as well, a condition obtains wherein the cleavages 

 are for the most part limited to the nuclei, which seem to multiply 

 for a time with great rapidity till a superficial layer is formed about 

 the entire surface of the egg. This layer is not however uniform 

 over the surface till a comparatively late stage. It seems to begin 

 usually at a given area, presumably richer in protoplasm and to 

 gradually extend to the remoter parts. Coincident with the extension 

 of these nuclear bodies, for there are not as yet any evidences of 

 cell boundaries, the egg at this time being in fact a syncytium, and 

 continuing such during the entire period of egg development, over 

 the surface, there has also been an extension between the yolk balls, 



