68 THE MAMMALIAN EGG 



In mammalian eggs, only the spindle is easily detected, though 

 the likelihood is that the form and function of the division apparatus 

 resemble those in non-mammalian eggs. The spindle can be seen 

 in living eggs, with the aid of phase-contrast microscopy, as well as 



Fig. 57 

 First polar body and metaphase second-meiotic spindle in an egt 

 of the golden hamster. X 1,200. (From Austin, 1956d.) 



Figs. 58 and 59 

 First cleavage spindle of the field-vole egg at metaphase, seen in 

 equatorial and polar views, respectively. The X chromosome is clearly 

 recognizable. X ca. 900. (From Austin, 1957b.) 



in fixed and stained preparations (Figs. 39, 40 and 55 to 58). In both 

 instances, the spindle presents itself as a transparent body, often with 

 faint longitudinal striations, and its existence is chiefly evident 

 through the absence of cytoplasmic particles. The refractility of the 

 component fibres is responsible for the stranded appearance; the 

 birefringence of the spindle in polarized light testifies to its con- 

 struction of longitudinally-orientated submicroscopic micelles. Late 

 anaphase and telophase spindles in eggs usually carry at the equator 

 a disc-shaped aggregation of granules constituting the intermediary 

 body (see also pp. 72 and 73). In ultrastructure, this body was found 

 to contain units made up of a pair of parallel membranes separated 



