The Fertilization and Early Development of the Pigeon's Egg

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. 1902. Excerpt: ... EXPLANATION OF DIAGRAMS 1-6. Diagram 1. Diagram showing number and relative position of accessory nuclei in the egg. The male and female pronuclei are in the center, lying in contact. Two sperm nuclei nearer than the rest. Same egg as in Fig. 11. xio. Diagram 2. Pronuclei in closer contact. Same egg as shown In Fig. 12. Owing to the incompleteness of the series the number of sperm nuclei Is too small, x 10 Diageam 3. Stage of segmentation nucleus. Accessory nuclei are mostly In pairs, indicating previous division. Same egg as Fig. 13. x W. Diagram 4. Stage of first cleavage spindle. Same egg as Fig. 14. X 10 Diagram 5. First furrow is beginning to appear at surface (f). The two cleavage nuclei equidistant. Same egg as in Fig. 15. x 10 Diagram 6. Beginning of second division. The accessory nuclei appear nearer the center of the disc than in the previous stage, x 10 phenomena and amceboid movements occurring on the surface of the egg along the circle whose plane separates the two astral systems. The Early Cleavages.--In Figs. 40-45 are shown the 2-4-8-16 cell stages, drawn from a surface view. The accessory cleavage is also shown, except in the sixteen-cell stage. The first furrow crosses the disc along its shorter diameter. It is slightly eccentric in position. In the four-cell stage is seen the so-called cross furrow connecting the second furrows. In the eight-cell stage, considerable variety exists in the position of the furrows. A more regular type is shown in Fig. 43, and an irregular one in Fig. 42. The more regular type shows meridional furrows at quite corresponding positions in the four quadrants. In the sixteen-cell stage shown the accessory cleavage is not represented (Fig. 45). The nuclei in the anaphase of division are shown as they appeared...