54 FRANK R. LILLIE. 



Thus the operation destroyed in each case not only definite 

 somites, but also all posterior to the first one injured, and the body 

 wall lateral to the somites. With more refined methods, it may 

 be possible to eliminate single somites from within the series, and 

 to avoid injury to adjacent tissues. Such a technique would en- 

 able one to analyze many of the problems offered by the somites : 

 to determine, for instance, the exact part played by them in devel- 

 opment of the limbs, the order of origin of the most anterior 

 somites, etc. Such problems are now being studied with partial 

 success, and the results will be published later. 



UNIVERSITY OF CHICAGO, 

 March, 1904. 



