8 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 striz 
