Problems of fertilization / by Frank Rattray Lillie.

  • Lillie, Frank Rattray, 1870-1947.
Date:
[1919], ©1919
Catalogue details

Licence: Public Domain Mark

Credit: Problems of fertilization / by Frank Rattray Lillie. Source: Wellcome Collection.

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    of cell division was accurately ascertained and applied to the genealogy of the germ cells, until the respective parts of ovum and spermatozoon in the origin of the new generation were understood, nor until the hoary doctrine of spontaneous generation was banished bodily from the field of biology. These were all accomplishments of that great decade in biological research (1870-80), for which the studies of the preceding thirty years had furnished ample preparation. The entire superstructure of modern genetic research rests upon the foundations then laid. Professor Mark’s paper on Limax (1881) is a point of departure between the fertilization studies of the seventies and those that were to follow. Professor Mark observed that the pronuclei come together but do not fuse to form a first cleavage nucleus, as had been described for other animals. ‘‘The first cleavage nucleus does not have a morphological existence.” The pro- nuclei persist after the appearance of the cleavage centers; their membranes then gradually disappear. In 1883 Van Beneden published his now classic paper on A scans. The pronuclei do not fuse; both are included in a single amphiaster; each produces two chromosomes; these divide and their halves form the daughter-nuclei. In the nuclei of the first two cells there are thus equal numbers of male and female elements; and there are reasons to believe that even in these two nuclei they do not fuse; it is probable that they remain distinct in all derivative cells, including the immature eggs and spermatogonia. In the egg the chromatin is composed of two distinct parts, and “it is legitimate to suppose that each is the equivalent of a male and a