210 Dr Martin Barry on the 



After this assimilative process has continued 

 for a sufficient length of time, that which has ^^' 



become the nucleus divides into two halves (fig. 

 17) ; which two halves, by appropriating the / r> 

 result of this cell-formation, and by the same \ ^ 

 process as that above described, are enabled 

 (fig. 18) to give origin to two cells, intended 

 to succeed the parent. (For each of the two halves just men- 

 tioned is a globule of hyaline, such as the 

 largest of those in the woodcut fig. 1 ; gra- ^^^' ^^' 

 dually becoming (figs. 2, 3) a cytoblast (fig. 4), 

 and then a cell (fig. 5) ; and the nucleus of 

 this cell presents a repetition of the same 

 process as that bringing successively into 

 view, figs. 6 to 15 ; which should be rapidly 

 glanced over in their numerical oi*der, the eye being directed 

 to the ever active central hyaline.)* 



The mysterious hyaline centre of a nucleus, that is to say, 

 the centre of the germinal spot, exercising an 

 attractive force, is thus the point of fecundation ^^S* ^^' 

 in the ovum ; and assimilation having been 

 effected, and division of the nucleus accom- 

 plished, and the membrane of the germinal 

 vesicle, as well as all the transitory cells, hav- 

 ing disappeared by liquefaction, two cells remain (fig. 19), 

 the foundation of the new being. 



Of the further changes induced by fecundation, the follow- 

 ing is an outline. After cleavage, the nucleus 

 of each twin cell (fig. 19), gives origin to two ^^^* * 

 other cells (the membranes of the parent-cells 

 undergoing liquefaction), so that the foundation 

 of the new being now consists of four cells, fig. 

 20. After cleavage of the nuclei of these four, 

 there arise, in like manner, eight (fig. 21) ; and a continuation 



* During these changes, the germinal vesicle enlarges at the expense of the 

 so-called yelk, until it comes to occupy almost the entire ovum. 



