Embryology. 113 
beautifully ordered, that to my mind they constitute 
the most wonderful—if not also the most suggestive 
—which have ever been revealed by microscopical re- 
search. It is needless to say that I refer to the 
phenomena of karyokinesis. A few pages further on 
they will be described more fully. For our present 
purposes it is sufficient to give merely a pictorial 
Fic. 29.—Successive stages in the division of the ovum, or egg-cell, of 
aworm. (After Strasburger.) @ to d show the changes taking place in 
the nucleus and surrounding cell-contents, which result in the first 
segmentation of the ovum at e: f and g show a repetition of these 
changes in each of the two resulting cells, leading to the second seg- 
mentation stage at 4. 
illustration of their successive phases ; for a glance at 
such a representation serves to reveal the only point to 
which attention has now to be drawn—namely, the 
immense complexity of the processes in question, and 
therefore the contrast which they furnish to the simple 
(or “direct”) division of the nucleus preparatory to 
cell-division in the unicellular organisms. Here, then 
* I, 
