Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 FIG. 104.—Unequal segmentation of the Frog's egg (after Ecker) in ten successive stages. and larger portion, in which the segmentation proceeds much more slowly than in the former. In partial segmentation we find a sharply marked contrast between the formative and nutritive parts of the -' egg, inasmuch as the latter does not seg- ment. The terms holoblastic and me- roblastic therefore have been applied to total and partial seg- mentation respec- tively. Nevertheless, in total segmentati
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 FIG. 104.—Unequal segmentation of the Frog's egg (after Ecker) in ten successive stages. and larger portion, in which the segmentation proceeds much more slowly than in the former. In partial segmentation we find a sharply marked contrast between the formative and nutritive parts of the -' egg, inasmuch as the latter does not seg- ment. The terms holoblastic and me- roblastic therefore have been applied to total and partial seg- mentation respec- tively. Nevertheless, in total segmentation also, either groups of segments of a definite quality, or, at any rate, a fluid yolk material may be used for the nourishment of the developing embryo. In fact, the contents of every egg consists of two parts—(1) of a viscous albu- minous protoplasm; and (2) of a fatty granular matter, the deutoplasm, or food yolk. The first is derived from the protoplasm FIG. 105. Segmentation of the germinal disc of a Fowl's egg, surface view (after Kolliker). A, germinal disc with the first vertical furrow ; B, the same with two vertical furrows crossing one another at right angles; C and I), more ad- vanced stages with small central segments.
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