STRUCTURE AND FUNCTION IN MAMMALIAN EGGS 



51 



apparent that a system, resembling in certain respects the nucleolus- 

 associated-chromatin system of Caspersson (1950), becomes increas- 

 ingly more evident as cleavage proceeds. Not until implantation 



231 ♦> 



£ 



v : 



Fig. 34 



Nuclei in rat eggs: (a) 4-cell, (b), (c) and (e) to (j) 8-cell, (d) 16-cell. Photographs in (/), 

 (//) and(j) were taken by ultra-violet microscopy at 2,600 A, the remainder by phase-contrast. 

 (<*)-(</) X 2,000. (e)-(j') X 900. (From Austin, 1953.) 



