blastula

The hollow sphere which is thus formed is the important stage of the “germinal vesicle,” the blastula, or blastosphere.

Consider its mode of division, and the formation of the blastula, gastrula, and germinal layers.

In a blastula showing complete segmentation the blastomeres of the upper hemisphere are the more finely subdivided.

Our next question concerns the distribution of potentiality, when the embryo is developed further than the blastula stage.

But there is in the blastula no trace of one part of the germ becoming different with respect to others of its parts.