SEGMENTATION OF THE OVUM OF THE SHEEP. 209 



acid stained with carmalum, cut aud mounted iu series of 

 sections. Each specimen proved to be on the point of com- 

 pletion of the process of fertilisation. 



PI. 15, fig. 2, is a section of one of these two. The section 

 passes through both male aud female pronucleus. 



I have not been able to identify a polar body. The contents 

 of the ovum are for the most part of a very uniform texture. 

 At three points, however, the granulations are coarser and 

 more concentrated and are more deeply stained. The section 

 passes through two of these. The third, which is the least 

 conspicuous, is at the periphery opposite, and the next section 

 passes through it. 



The accumulation of deeply staining particles envelops the 

 inner face of one pronucleus only. The opposing face of the 

 other pronucleus seems to be surrounded by a less concen- 

 trated area. Close to this latter nucleus is a small, round, 

 deeply staining body, which does not occur in the section from 

 which fig. 1 has been drawn. The other specimen mentioned 

 above is in exactly the same condition, and presents the same 

 features, with the exception that the small deeply staining 

 body is not present. This specimen is cut iu a plane at right 

 angles to the previously described section. 



In this specimen and in others there are certain spherical 

 bodies near to the periphery of the cell, which stain rather 

 deeply and homogeneously. They appear to be of the nature 

 of yolk granules, and are shown in my drawing of the next 

 specimen which I shall describe. 



This one (fig. 3) was presumably about two days old, and 

 was found halfway down the oviduct. It was cut into sections, 

 aud was found to be in the act of dividing. The plane of the 

 section is, I think, at right angles to the direction of the 

 spindle. The chromatin threads are arranged near the centre 

 of the ovum. The spherical bodies mentioned above, two of 

 which can be seen at Y in my figure, are not scattered so evenly 

 over the surface of the ovum as in the former stage. They are 

 all close to the surface, and are aggregated round the two poles. 

 There are rather more in one hemisphere than iu the other — 



