STRUCTURE AND FUNCTION IN MAMMALIAN EGGS 



71 



the 2-cell egg (Odor and Blandau, 1951b). In the earliest stages of 

 the transformation of the sperm head into the male pronucleus, the 

 perforatorium appears to have a third prong, originally lying along 



w 



■- 



• * g 



Fig. 61 

 Sperm tails in the eggs of (a) the Libyan jird, and (b) the golden hamster. The mid-piece 

 appears to be disintegrating in the manner of a thread becoming unwound. In (b), the 

 'smoke ring' is visible in the middle of the picture. X 1,800. ( (b) from Austin and Bishop, 

 1957b.) 



part of the greater curvature of the sperm head (Austin and Sapsford, 

 1952; Austin and Bishop, 1958b); this conforms with its description 

 in the intact spermatozoon as a modified part of the nuclear mem- 

 brane (Leblond and Clermont, 1952a, b). The continuity of the 

 perforatorium with the rest of the nuclear membrane can be made 

 out a little more easily in the hamster egg (Austin and Bishop, 1958c). 



