The eggs of the Decapods, after exclusion from the genital organs, pass back, and are attached to the abdominal feet of the mother, where they undergo a portion of their development.

The eggs of the Decapods have a regular segmentation, but, owing to the fact that the protoplasm has a perpheral distribution, the planes of cleavage do not pass completely through the egg.

When the segmentation is completed, a small patch of the blastoderm invaginates to form the primitive stomach, and the opening or blastopore soon closes.

By similar imaginations the anterior and posterior portions of the digestive tract are formed, each pushing in until it meets the first invagination.

Anticipating for a moment our account, we will say that here, as in all Crustacea, the primitive stomach, or mesenteron of embryologists, foi-ms but a very small portion of the alimentary tract, and that from the anterior invagination, the stomodeum, as it is called, the stomach with its complicated mill is developed.