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On the Maturation of the Ovum in the Guinea-prg. 
By J. E. Satvin Moors, A.R.C.S., F.L.S., Professor of Experimental and 
Pathological Cytology, Liverpool, and Miss F. Tozgr, B.Sc. London. 
(From the Cytological Department of the University of Liverpool.) 
(Communicated by J. Bretland Farmer, F.R.S. Received January 14,—Read 
February 27, 1908.) 
[PLates 5—7.] 
The following observations on the maturation of the ovum in the Guinea- 
pig are related to a more extended investigation. Certain results which 
we have already obtained while investigating the development of the eggs 
of the Guinea-pig are, however, of interest, and we think it desirable to 
give a brief account of them.* In the earlier stages of the development 
of the eggs within the ovary they appear as cells which present within 
their nuclei the characteristic synaptic contraction of the nuclear thread- 
work. Occasionally, during such stages, the centrosomes are clearly visible 
within a definite archoplasm. As the eggs increase in size the centrosomes 
appear to migrate from the interior of the archoplasm into the cytoplasm 
this migration corresponding to the migration of the centrosomes in similar 
stages in the development of spermatozoa. At a later period in the develop- 
ment, both archoplasm and centrosomes in the eggs disappear altogether. 
The development of the egg is nearly complete within the ovary. That is 
to say, the two maturation spindles corresponding to the maturation spindles 
in the production of the spermatozoa are found while the eggs are enclosed 
in the follicle and are still retained in the ovary. 
When the eggs have reached the large size represented in Plate 5, 1, the final 
stages in the evolution of a coarse spirem, corresponding to the coarse spirem 
of the spermatogenesis, are reached, and in the succeeding phase there occurs the 
usual development of gemini within the nucleus. Ina large number of the eggs 
the gemini appear to result from the pairing of the number of chromosomes 
usually found in somatic cells ; but it is very important to note that in many of 
the eggs with which we have had to deal the number of the aggregates of 
chromatin is largely in excess of what it ought to be, supposing these bodies 
* A detailed account of the early development of the egg in mammals is given by 
Winiwarter (“ Recherches sur ’Ovogenése et ’Organogenése de l’Ovaire des Mammiféres 
(Lapin et Homme),” par le Dr. Hans von Winiwarter, ‘Archives de Biologie,’ vol. 17, 
1900). An account of the fertilisation and segmentation of the eggs of the Mouse is 
contained in a paper by Sobotta in the ‘ Arch. f. Mikr. Anat.,’ vol. 45, 1895. 
