>a 'd 



Figure 41. Comparison of Warnek's designations of blastcraeres 

 (stage numbers) with the recent literal-numerical 

 designations of blastomeres . These and the other 

 designations are put in the contours of Warnek's 

 drawings . 



During the development of the embryo, further changes of 

 chemical processes take place. 



The gastropodan molluscs are characterized by complete 

 division. 



The globules of division may be considered true cells. 



In each stage of a division process four yolk globules 

 are formed, i.e. the division proceeds not in geometrical, 

 but in arithmetical progression. 



Beginning with the third stage, the globules of division 

 have unlike sizes. 



559 



