108 L. DONOASTEI?. 



even if this is found to he a phenomenon of general occurrence 

 it does not necessarily affect the hypothesis of the individuality 

 of the chromosomes in any essential point. 



Chromosomes in the Maturation Divisions of the Egg. 



It has now been shown that in the spermatogonia! and 

 oogonial divisions there are eight chromosomes, and that in 

 the spermatocytes these are reduced to four in the normal 

 heterotype manner. These facts led me to re-investigate the 

 maturation divisions of the eo;g, since in my previous paper 

 (loo. cit.) I gave evidence that in both first and second polar 

 mitoses the number was eight. 



The chromosomes in the maturation of the egg are much 

 less easy to observe than in the spermatogenesis, for there 

 are difficulties of technique to be overcome, and the egg has 

 to be preserved at exactly the right moment. But after 

 cutting some hundreds of eggs I have been able to convince 

 myself that while there are two types of maturation. In some 

 eggs no reduction takes place, and eight chromosomes pass 

 into each of the four nuclei produced by the polar mitosis. 

 In other eggs four double chromosomes are found in the 

 equatorial plate of the second maturation division, and these 

 sepai'ate into their component halves sending four into each 

 daughter-nucleus (figs. 17 — 21). 



I have never obtained a section of the first polar mitosis in 

 which it is quite certain that there are four '' gemini," although 

 some figures strongly suggest this ; but at the close of the 

 first division, when the chromosomes are arranging themselves 

 to form the equatorial plate of the second mitosis, four double 

 chromosomes are sometimes clearly visible (figs. 20, 21). I 

 have also several preparations which show only four when the 

 second polar mitosis is already begun. A comparison of figs. 

 17 and 19, 18 and 20, respectively, will show the difference 

 between the reducing and equational types of maturation. 



It must therefore be concluded that in some eggs pairing 



