CHAPTER I.
THE OVUM AND SPERMATOZOON.
The Ovum.
The complete developmental history of any being constitutes a cycle. It is therefore permissible in treating of this history to begin at any point. As a matter of convenience the ovum appears to be the most suitable point of departure. The question as to the germinal layer from which it is ultimately derived is dealt with in a subsequent part of the work; the present chapter deals with its origin and growth.
General History of the Ovum.
Every young ovum ([fig. 1]) has the character of a simple cell. It is formed of a mass of naked protoplasm (a), containing in its interior a nucleus (b), within which there is a nucleolus (c). The nucleus and nucleolus are usually known as the germinal vesicle and germinal spot.
Fig. 1. Diagram Of the Ovum. (From Gegenbaur.)