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Formerly it was said that the head consisted of four divisions, viz. three segments and the procephalic or prae-oral lobes.

It is now ascertained that the procephalic lobes consist of three divisions, so that the head must certainly be formed from at least six segments.

But the protocerebrum contains the ganglia of the ocular segment in addition to those of the procephalic lobes.

Procephalic, prō-se-fal′ik, or prō-sef′a-lik, adj. of or pertaining to the forepart of the head.—Procephalic lobes, two lobes in the embryo of the Podophthalmia which develop into the anterior parts of the head.

This portion is divided by a median fissure into two lobes, which play an important part 45in the development of the head, and will be termed the ‘procephalic lobes.’