252 Action of the Genetic Material 



of the type belonging to the stalk out of which it grew but of the 

 type which supplied the nucleus. It must thus be concluded that the 

 formative substances produced by the nucleus, controlling the charac- 

 ter of the species in regard to the structure of the umbrella, are the 

 result of genie action. Here, then, we have in the simplest form, within 

 one cell, the general type of genie action which we have postulated: 

 production by the genie material of an active, diffusible substance 



Cops: 



n.h. 



A 



I . Group 



en. top 



en. h. 



■olwoys frequ. rore 



A-0.25( 



-1.50 cm. 



/lA» 



2. Group 

 medQwettst, wetlst^med, 



medo 



wettsto 



,wettst| Tmed| 



e f 



wettst-cop med-cop 



creni med| 

 acici med| 



/k regenerate 



creni med| 

 (ocic,) 

 9 



Cop: intern). 



4. Group 

 cren, ociC| 



creni ociC| ^ 



h 

 cren and oc. 



creni polyi 

 med| poIyi 

 medi wetfsti 



**■' creni polyi^ 



med 



I (weltst,) 

 obn. 



en. top — enucleated top piece 



— nucleated 



— enucleated hind piece 



Figs. 14, 15. Diagrams of basic experiments with Acetabularia. (From Ham- 



merling, 1953.) 



which controls the specificity of a morphogenetic feature. If this 

 substance could be analyzed chemically, we should have the right to 

 speak of the isolation of Genwirkstoffe. (See, below, Brachet's work 

 on the nature of these substances and discussion of his theories; also 

 new contributions by Hammerling. ) In this case, moreover, it is not 

 the decision of an independently inherited alternative, as in the model 

 of the sex hormones, but a direct and specific morphogenetic deter- 

 mination at a given point of a single though morphologically compli- 

 cated cell. It will be well to keep this in mind for the subsequent 



