320 



GENERAL PRINCIPLES 



696. Ill the development of the egg the process is similar to 

 that of the sperm up to the period of growth. The mother cell 

 of the egg continues to grow for a long time, so that a cell of 

 comparatively gigantic proportions results. When the nucleus 

 proceeds to divide, four pairs of chromosomes appear, as in the 



FIG. 183. Diagram illustrating the reduction of the chromosomes during 

 spermatogenesis. (McMurrich.) sc l , Spermatocyte of the first order; sc 2 , 

 spermatocyte of the second order; sp, spermatid. The number of the chromo- 

 somes is supposed to be 8( = 2x) in the zygote, and 4( = x) in the gametes. 



sperm mother cell, and they are likewise arranged in two groups 

 of four. The nucleus, however, comes to the surface of the cell 

 and the spindle takes a radial position, so that on division of 

 the cell there results one very small cell (first polar body) and 

 one very large one. Then, as in the case of the sperm, the 



