Abstract
It has been noted in atretic follicles of ovaries of a number of different mammals that the oocytes appear to be going through a process closely resembling normal development. It appears to be a matter of interpretation, after a review of the literature from 1884-1930, as to whether this process is the beginning of parthenogenetic cleavage or whether it is only degenerative fragmentation.
Segmented ovarian ova appeared in every stage of the oestrous cycle of the white rat. They were more numerous in pregnant rats which were at the fifth and eighteenth day of their gestation period. This observation agrees with that of Evans and Swezy. 1 The small size of the follicle and of the segmented egg within, in comparison with the normal follicle and egg is striking. The abnormal follicles were in every case below the surface of the ovary, and in nearly every case they were adjacent to larger normal follicles, or to ovarian corpora. Swezy 2 found very few follicles developing from the germinal epithelium bounding follicles or corpora, due she believed, to the tension exerted by the expanding body beneath. As the normal follicle enlarges it pushes out in lobules and due to these outpushings on the part of the normal follicle normal growth and development is denied the smaller adjacent follicles. As pressure is increased upon a follicle there is a corresponding increase in pressure upon the ovum within. It seems probable that this increase in pressure has some effect upon the initiation of the development of the egg.
In 39 of the 42 cases studied the segmented ova had a constant diameter of either 0.0428 mm. or 0.0570 mm. Kirkham and Burr 3 gave the diameter of the living unsegmented egg as of 0.079 mm.
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