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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt:...but close to the animal pole, so that the division is very unequal. Irregularities in this cleavage are very numerous. E. Later Segmentation Stages (see plate, Figs. 16-24).--The later divisions occur with increasing rapidity, but with such irregularity that no definite arrangement of cleavage furrows can be made out. Cleavage proceeds rapidly near the animal pole, much more slowly in the equatorial region, and is greatly retarded in the lower hemisphere. At some time during the second day after the egg is laid the first cleavage furrow reaches the lower pole. At this time the upper hemisphere is cut up into a considerable number of cells. The macromeres continue to be very much larger than the micromeres. While so far as can be determined from a surface study of the egg, the cleavage is undoubtedly holoblastic, a strong tendency toward the meroblastic condition is evident. Two days after the egg is laid, cell division in the upper hemisphere has advanced until the individual cells can no longer be seen with the naked eye. The macromeres are in general still quite large, but in several instances there was noted a greater multiplication of cells about the lower pole than in the equatorial region (see Fig. 24B). F. Comparison with Other Forms.--De Bussy ('05) has described the principal segmentation stages of the eggs of C. japonicus. His material lacked eggs in the 2-cell and 4-cell condition; but beginning with the 8-cell stage the later cleavage stages are described and illustrated. A comparison with my own sketches of the segmentation of the eggs of Cryptobranchns allcgheniensis, made before I knew of the existence of de Bussy's paper on C. japonicus, shows, as might be expected from the close relationship of the two forms, a marked similarity in the mode...