XI. ON THE PHENOMENA ACCOMPANYING THE MATURATION 

 AND IMPREGNATION OF THE OvuM 1 . 



THE brilliant discoveries of Strasburger and Auerbach have 

 caused the attention of a large number of biologists to be turned 

 to the phenomena accompanying the division of nuclei and the 

 maturation and impregnation of the ovum. The results of the 

 recent investigations on the first of these points formed the sub- 

 ject of an article by Mr Priestley in the sixteenth volume of this 

 Journal, and the object of the present article is to give some 

 account of what has so far been made out with reference to the 

 second of them. The matters to be treated of naturally fall 

 under two heads: (i) the changes attending the ripening of the 

 ovum, wJiich are independent of impregnation ; (2) the changes 

 which are directly due to impregnation. 



Every ovum as it approaches maturity is found to be composed 

 (Fig. i) of (i) a protoplasmic body or vitellus usually containing 

 yolk-spherules in suspension; (2) of a germinal vesicle or nucleus, 



FIG. i. Unripe ovum of Toxopneustes lividus (copied from Hertwig). 

 1 From the Quarterly Journal of Microscopical Science, April, 1878. 



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