Excerpt from On Turritopsis Nutricula (McCrady)

The primitive ova grow by the absorption of the ovarian cells around them. As growth takes place there is a change in the character of the cytoplasm. It loses its homogeneous and finely granular nature and develops a supply of deuteroplasm in the form of yolk granules. These are large and stain very darkly. They first appear around the germinal vesicle. As they become more numerous by the continual formation of new ones, they are pushed out through the cytoplasm toward the periphery. The formation Of the volk spheres goes on until the ovum is densely crowded with them except for a narrow peripheral zone, in which the protoplasm retains its homogeneous and finely granular character and forms the ectoplasm of the mature egg. Figures 10 to 15 Of plate 32 show different stages in the develop ment of the ovarian egg and the formation and migration Of the yolk granules. Some idea of the extent to which the protoplasm becomes crowded with spheres of deuteroplasm can be formed from figure 15 (pl. 32) which is drawn from a nearly mature ovum. In the fully developed egg the layer of ectoplasm is narrower than represented in this figure.

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