249 



character of an organism corresponds to one or more enzymes, which exert a reaction 

 on specific substrates. 



Long ago already I came to the conviction that the ontogenetic evolution of the 

 higher plants and animals can be best explained by admitting that it is caused hy a 

 series of enzymes, for the greater part endoenzymes, which, becoming active in a 

 fixed succession, determine the morphological and physiological properties gradually 

 manifest in the development. These enzymes in the formation of plant-galls are 

 likewise concerned, and in a study on the galls of the saw-fly Nematus capreae on the 

 leaves of Sali.v amygdalina, I gave them the name of growth enzymes 1 ). It is still 

 my opinion that this view is in the main 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 introduce enzymes into it. 



Research material. 



In the free living unicellular organisms morphological differentiation, joined with 

 cell division, is quite or almost quite absent, which much simplifies the ontogenetic 

 development. That in this case the properties must be represented just in the same 

 way by specific factors, that is by heredity units or Mendelian factors, as in the 

 cell protoplasm of the higher organisms, is beyond question. Although it would be 

 erroneous to admit that the number of characters, and so of the heredity units or 

 factors of the unicellular organisms must be small, we certainly have to deal here 

 with a simpler case than in the multicellular. Hence it seemed probable that heredity 

 experiments with the former would give some chance better to understand the nature 

 of the heredity units in general. 



But not all properties are equally well adapted to such a research. To show that 

 some character of a cell corresponds to one or more units or Mendelian factors, 

 that character must be able to change by mutability in such a way that the mutants 

 prove to be hereditary constant races, distinctly different from the original form, for 

 the conception of heredity units must also for the unicellulars start from the possi- 

 bility of race formation. 



The character to be studied must further be observable with ease and accuracy 

 and it must be possible to cultivate the concerned organism in a simple way, so that 

 in few days thousands of individuals can be examined and that no doubt is left as to their 

 distinction from foreign infections. These requirements are very well answered by 

 some pigment- and by the luminous bacteria as I repeatedly stated before 2 ). Espe- 



thus: Herr W. Kuhne berichtet iiber das Verhalten verschiedener organisirter und 

 sogenannter imgeformter Fermente. Um Missverstandnissen vorzubeugen und lastige 

 Umschreibungen zu vermeiden, schlagt Vortragender vor, die ungeformten oder nicht- 

 organisirten Fermente, deren Wirkung ohne Anwesenheit von Organismen oder ausser- 

 halb derselben erfolgen kann, als Enzyme zu bezeichnen. This proposal is still acceptable. 

 That Kuhne only thought of exoenzymes was in accordance with the times. The term 

 endoenzyme was introduced in 1900 by M. H ahn (Zeitschr f. Biologic Bd. 40 pag. 172, 

 1900). But the conception existed already long before. Enzyme comes from the Greek 

 en in, and zyme leaven, and is related to zeo I boil. 



*) Das Cecidium von Nematus capreae auf Salix amygdalina. Botan. Zeitung 1888, pag. i. 



-) These Proceedings, 21 November 1900 and 9 February 1910. 



