OF ENVIRONMENT 139 



would be susceptible to modification in the stage 

 between the reduction divisions and fertilization. 



This conclusion is borne out by my own results 

 in which solutions were introduced into the ovary 

 during this stage. The extent of the treatments, 

 together with the diversity of results, makes pos- 

 sible an analysis of other features. Thus the in- 

 duction of more than one form by the use of a 

 single reagent suggests either that different chro- 

 matin elements were affected in the separate 

 ovular reactions, or that unhke parts of the chains 

 of catalytic action were interrupted or disturbed 

 by the introduced substances. Some of the com- 

 pounds used are inimical to enzymatic action, or 

 may be capable of a negatively catalytic effect, 

 or might indeed set up unusual splitting proc- 

 esses, a state of affairs distinctly favorable to the 

 last named alternative. 



Not only may irradiation and the introduction 

 of unusual substances occur naturally to the mod- 

 ification of heredity in plants, but the climatic 

 factors may, as in Tower's experiments, exercise 

 an influence upon the reaction velocities of va- 

 rious parts of the metabolic series, or by varia- 

 tions in humidity, regulate the excretion or reten- 

 tion of active substances. All of these possibihties 

 must be taken into account in attempts at expla- 

 nation of bud-sports or bud-mutations in plants. 

 It is to be seen that either egg or sperm may be 

 affected by experimental agencies, and that the 

 results do not differ in quahty or degree. Gager's 



