SYNAPSIS IN THE EGG OF THE WHITE RAT 453 



be distinguished in a fairly large percentage of the cells, but it 

 has not been found in any of the nuclei of the later stages. It 

 will be seen that this body is evident throughout the period in the 

 process of synapsis, when there is a distinct orientation of the 

 chromatin threads. This orientation seems to have a definite 

 relation to the position of the centrosome, the bent portion of 

 the loops being, in all clear cases, directed away from that side 

 of the cell where it occurs (fig. 12). As has already been clearly 

 pointed out (von Winiwarter and Sainmont, '08) it cannot be 

 asserted on the evidence here available that this body actually is 

 the centrosome and its enclosed granule the centriole. On the 

 other hand the converse is just as difficult of demonstration. 



The chromatoid body here referred to is a deeply staining 

 body of small size appearing, seemingly, in any region of the cyto- 

 plasm. It is rarely to be found in the cells with synaptene nuclei. 

 During the pachytene stage (figs. 12 and 15) it is common, and 

 here not infrequently two such bodies may be found in the same 

 cell. From this time on throughout the period involved in this 

 paper, it is a constant feature of a large percentage of the cells. 

 During later stages there may be quite a number of these bodies 

 (text fig. 2). Neither the origin nor the fate of these two 

 structures has been determined. 



DISCUSSION AND CONCLUSIONS 



As a whole the series of changes associated with synapsis in 

 the egg. of the rat rather closely resembles the same period of 

 development in other mammals carefully studied (von Wini- 

 warter, '00, and von Winiwarter and Sainmont, '08). There are, 

 however, some very noticeable differences. Those changes 

 taking place subsequent to the last oogonial division and just 

 previous to the formation of the leptotene threads, are much 

 more elaborate in the rat than in any of the other forms de- 

 scribed. In the case of the cat there is some shght suggestion in 

 the figures (von Winiwarter and Sainmont, '08) of such a series 

 of changes but they seem much less complex than in the rat. 

 Particularly in the rabbit and in man there is a complete ab- 

 sence of those transition nuclei with the chromatin in irregular 



