70 



INDIVIDUALITY IN ORGANISMS 



progressing posteriorly, the successive formation of the 

 somites or segments being a conspicuous feature of this 

 progress. Fig. i6 is a transverse section of an early 



Figs. 14, 15. — Surface views of two early stages in embryonic 

 development of chick, showing progress of development in basal direction 

 from the head-region (upper end) and laterally from the median region; 

 s, somites (from F. R. Lillie). 



stage before distinct organs have begun to form. At 

 this time cells are separating from the outer layer of 

 the body in what will later become the median dorsal 



