Artificial parthenogenesis and fertilisation : a review / by Thomas H. Bryce.

  • Thomas Hastie Bryce
Date:
[1902]
Catalogue details

Licence: In copyright

Credit: Artificial parthenogenesis and fertilisation : a review / by Thomas H. Bryce. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    22/31 page 499
    alternate changes of disintegration and reconstruction with- out division of the cytoplasm. Radiations appeared and dis- appeared, and after three cycles, owing to the segmentation of the portions containing the sperm nucleus, the egg-nuclear portion became detached and disintegrated. In another experiment the egg-nuclear portion underwent changes of form suggesting abortive attempts at cleavage. The mitotic transformation of the egg nucleus was not synchronous with that of the sperm nucleus, but always a little behind. These observations show that under the conditions of the experiments the egg nucleus is excited to division without direct contact with the sperm nucleus or aster, but that the mitotic phenomena are ineffective to produce cytoplasmic cleavage. Ziegler refers this to the general stimulation of the egg by the spermatozoon, manifested also by the throw- ing off of the vitelline membrane. Boveri has shown that the same phenomena occur in egg fragments produced by slinking some minutes after fertilisation, and he (1902) refers to cases of this kind in which he has observed divisions of the nucleus followed by cell cleavage. The division was repeated a second time, and thus the four-cell stage was reached, but development then ceased. Another example of the effect of this general stimulation is to be seen (Boveri, 1902) in the cases in which the egg is incited to throw off the polar bodies by the entrance of the spermatozoon. This brings me to a further reference to Wilson’s observa- tions on etherised eggs (1901 b). As has already been said, under this treatment the sperm and germ nuclei remain apart and undergo independently karyokinetic transforma- tion. “ The most striking fact is that, while the sperm aster often gives rise to a perfect and symmetrical bipolar figure, the egg uucleus in a great number of cases produces a monaster, which seems at first incapable of resolving itself into a bipolar figure.” In typical cases the egg nucleus gives rise to a monaster such as described by Hertwig (’96), and such as occurs in magnesium eggs. While the egg monaster does not at first give rise to a dicentric figure, it does so later, as
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