60 ♦ 



correct, but while I formerly thought that the growth enzymes partly 

 derived from the gall-insect, I now recognize that they belong to the 

 plant only, and that the animal does not introducé enzymes into it." 

 It is apparent that Beijerinck's views have matured in 1917, but 

 that the principle underlying his considerations on cecidiogenesis and 

 ontogenesis of organisms has been unchanged. If one considers the 

 importance attached to hormones and auxins in modern morphology, 

 then one realizes that Beijerinck's considerations come close to the 

 newer views and that with respect to this problem as well as to many 

 others he was far ahead of his time. 



