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 sufificient to give merely a pictorial 



Fig. 29. — Successive stages in the division of the ovum, or egg-cell, of 

 a worm. (After Strasburger.) a to d show the changes taking place in 

 the nucleus and surrounding cell-contents, which result in the first 

 segmentation of the ovum at <s : /" and g show a repetition of these 

 changes in each of the two resulting cells, leading to the second seg- 

 mentation stage at A. 



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 



