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In some forms, moreover, the broader fundamental features of embryogeny are already established before the entrance of the spermatozoon.

Presumably in early embryogeny, probably at the two-celled stage of cleavage, the two blastomeres become separated and each gives rise to a complete individual instead of only the half of one it would have produced had the two blastomeres remained together.

When once it is established that the morphoplasm of each cell is controlled, and its character decided, by the idioplasm of the nucleus, the regular changes occurring in the egg-cell, and the products of its division in each embryogeny, must then be referred to the corresponding changes of the idioplasm.'

The matter seemed involved in mystery, and no one attempted to raise the veil which hung over the subject of embryogeny.

Highmore's book is an important one in the history of embryology, since it is the first treatment of embryogeny from the atomistic viewpoint and because it contains the first published observations based upon microscopic examination of the chick blastoderm.