. The cell; outlines of general anatomy and physiology. Fig. 122.—Superficial cleavage of the egg of an insect (Pieris crataegi) (after Bobretsky;from R. Hertwig, Fig. 100) : A division of the cleavage nucleus; B the nuclei raisethemselves and commence to form a germinal layer (blastoderm); C formation of blas-toderm. follow. These THE VITAL PHENOMENA OF THE CELL ,j 233 daughter-nuclei {Fig. 122 J.) then divide into four, ^?y^-^^j^^these four into eight, the eight ? ^^^^^?-l^.:^-^$^ into sixteen, and so on, whilst the?egg as a whole remains unseg-mented. Later on the nuclei sepa-rate from one

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. The cell; outlines of general anatomy and physiology. Fig. 122.—Superficial cleavage of the egg of an insect (Pieris crataegi) (after Bobretsky;from R. Hertwig, Fig. 100) : A division of the cleavage nucleus; B the nuclei raisethemselves and commence to form a germinal layer (blastoderm); C formation of blas-toderm. follow. These THE VITAL PHENOMENA OF THE CELL ,j 233 daughter-nuclei {Fig. 122 J.) then divide into four, ^?y^-^^j^^these four into eight, the eight ? ^^^^^?-l^.:^-^$^ into sixteen, and so on, whilst the?egg as a whole remains unseg-mented. Later on the nuclei sepa-rate from one another, and for themost part move gradually to (Fig. 122 B), penetratinginto the protoplasmic envelope,where they arrange themselves at•equal distances from one until this has occurred doesthe egg commence to segment, theperipheral layer splitting up many cells as there are nuclei init, whilst the central yolk remainsintact, or is only split up at amuch later period. This latteroccurs when

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Keywords: ., bookcentury1800, bookdecade1890, bookidcelloutlines, bookyear1895