232 
J. p. LOTSY. 
,,We also know that iu many cases (it is merely a technical difficulty 
,,which prevents us frora verifying this for ail cases) tliese iiiheritable 
„tliings must be présent in ail the cells of tlie individual (one epidermis- 
,,cell of Bégonia can give rise to a complète plant) wearethereforeforced 
,^to admit that the inheritable thiiig, with which we are dealiiig is capa- 
,,ble of reproducing its kind/' 
La remarque suivante est aussi parfaitement exacte: 
,,The hypothesis that thèse hereditary things are vital units, composed 
^,of protoplasm and capable of assimilation and growth, certainly fits the 
^^facts, but we ask more of a theory of heredity and évolution. A work- 
„ing-hypothesis to be of any use as an instrument of reseauch must 
^^explain the facts in terms of what is already known. It is inadmissa- 
„ble to try to explain the facts of évolution and inheritance by the be- 
„haviour of living j^articles which bave been invented simply to admit 
,,of this explanation.'^ 
Il dit ensuite : 
„We must again look to the facts to try and find whether there is 
,,not a possibility that not the living being and ,,therefore" ail the cau- 
,,sating agents for its characters are living things, but that the orga- 
„nisms are living because the fact that tliey have ail the characters" 
(mieux vaudrait: because they have the causating agents for thèse cha- 
racters). 
Hagedoorn se demande alors: „Wliat then is the nature of thèse 
,,genetic factors?'' et il répond: 
„the hereditary factors for the development of an orgauism are nume- 
,,rous independently transmitted substances, each haviug autokatalytical 
,,properties." 
Cela est, à ce qu'il dit lui-même, simply a modification of the hypo- 
thèses of Loeb and Eoux, necessitated by the fact of Mendelian 
inheritance." 
Au sujet de ces hypothèses je renvoie au travail de Hagedoorn et 
à la bibliographie qu'on y trouvera. 
I/assertion suivante ') donnera une idée de la façon dont Hagedoorn 
se figure la chose: Il indique que l'on peut p. ex. filtrer la substance 
active des bacilles du tétanos et de la leviire et que ces parties essen- 
tielles des bactéries et des cellules de levure sont liées à ses organismes, 
') 1. c. p. 27. 
