. The development of the albino rat, Mus norvegicus albinus. Embryology -- Mammals; Rats. 28 G. CARL HUBER day after the beginning of insemination. During this period the segmented ova migrate in the oviduct for a distance equahng nearly half its length. The trustworthiness of the material, it would seem to me, is shown by the fact that in the shorter time stages the segmented ova are situated nearer the fimbriated end, while in the longer time stages they approach the region of the insertion of the oviduct into the uterine horn. This is clearly shown in the reconstructions shown in figures 7
. The development of the albino rat, Mus norvegicus albinus. Embryology -- Mammals; Rats. 28 G. CARL HUBER day after the beginning of insemination. During this period the segmented ova migrate in the oviduct for a distance equahng nearly half its length. The trustworthiness of the material, it would seem to me, is shown by the fact that in the shorter time stages the segmented ova are situated nearer the fimbriated end, while in the longer time stages they approach the region of the insertion of the oviduct into the uterine horn. This is clearly shown in the reconstructions shown in figures 7 and 8. A 3-cell stage was observed only twice: in one of eight ova contained in the oviducts of rat No. 58 (2 days, 17 hours) and in one of eleven ova found in the oviducts of rat No. 62 (2 days,. Fig. 11 Two views of each of three models of 4-cell stages of the albino rat. Rat No. 50, 3 days. 1 hour. X 200. A, B, and C, gives a side view, A', B', and C a vertical view, of each of the three models. 22 hours). All the other ova found in these two animals were in the 2-cell stage. In the two 3-cell stages noted, the undivided blastomeres of each ovum presented a nucleus in mitosis; in one, in the monaster phase, in one, in the diaster phase. The divi- sion of the first two blastomeres, resulting in the 4-cell stage, it would appear, occurs in the albino rat toward the end of the third day. The material gathered at the beginning of the fourth day after insemination presents throughout a 4-cell stage. In D of figure 1 is shown reproduced one of the sections of a series of six sections including one of the ova in the 3-cell stage. Only one of the two cells resulting from the division of one of the first two blastomeres is included in the section; the cell in mitosis represents the undivided Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not
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