Classification of the subsequent
middle-eyed, late-eyed, and very lateeyed
stages (stages 8–10; Fig. 1G–I) is
based on further differentiation of the
eyes, which parallels an increase in
the skin pigmentation of the head and
trunk. The middle-eyed embryo has
fully pigmented eyes (Fig. 1G),
whereas, in the late-eyed embryo, the
choroid covers most of the retina, and
rays of the dorsal, ventral, and caudal
fins have differentiated. The myotome
consists of approximately 30 somites