282 LILIAN SHELDON. 



a spindle, the chromatin representing the nuclear plate. The 

 spindle in this case is cut transversely to its long axis, the 

 section figured passing through the chromatin of the nuclear 

 plate. Fig. 11 represents a section through an ovum of similar 

 stage, in which the spindle is cut vertically ; in this case the 

 spindle lies with its long axis at right angles to the surface of 

 the ovum beneath which it lies. The same spindle is shown 

 more highly magnified in fig. 15. 



The spindle next changes its position so as to lie parallel 

 to the surface of the ovum ; this is shown in fig. 16. 



The chromatin of the nuclear plate separates into two layers, 

 a condition which is shown in fig, 17; and the two plates of 

 chromatin leave the centre of the spindle and gradually approach 

 its two ends respectively. A spindle at this stage is shown in 

 fig. 18. 



A protuberance now appears on the surface near one end of 

 the spindle, into which the latter passes, and by a gradual con- 

 striction this protuberance becomes separated off and forms 

 the first polar body, the chromatin of the spindle still remaining 

 clearly visible in it. Owing to the long axis of the spindle 

 being parallel to the surface of the ovum, the polar body does 

 not lie directly above but to one side of it (v. figs. 16 and 19). 



The nucleus now returns to a resting stage (v. figs. 19 and 

 20 a), when it has an oval form, stains slightly deeper than the 

 surrounding protoplasm, and contains several chromatin bodies. 

 It does not at this stage possess a clear or deeply staining wall. 

 The nucleus at this stage is shown in fig. 19, where also the 

 position of the first polar body, to one side of and not directly 

 above it, is also shown. 



The nucleus now again assumes the spindle form, and the 

 second polar body is formed in a manner exactly similar to 

 the first. 



In fig. 11 the male pronucleus is seen to be present lying at 

 the opposite side of the ovum from the germinal nucleus. It is 

 very small and oval^ and contains a small amount of chromatin. 

 It lies quite at the periphery of the ovum, close within the 

 eggshell. The protoplasm round it is marked with striae 



