198 PLANT HYBRIDIZATION BEFORE MENDEL 



growth, internal organization and external conformation, as well 

 as in the activities of the organism, are conditioned by number- 

 less differences in the chemical and plastic processes of the living 

 material, and by numberless combinations of the operative forces, 

 all of which are due to "the unlike form, size and arrangement 

 of the micellae of the idioplasm." (p. 26.) 



This being the case, then equality in respect to the inheritance, 

 is conditioned by the combining cells containing, on fertilization, 

 equal amounts of the idioplasmic material. Cases where a pre- 

 ponderance in the inheritance is on the side of the male or the 

 female parent, respectively, 



". . . must be explained through the fact that a greater quantity of 

 idioplasm occurs, now in the unfertilized egg cells, now in the sperma- 

 tozoa uniting with them." (p. 27.) 



The difference in potency of the idioplasm is indicated by the 

 fact that the male fertilization-plasma in the spermatozoid may 

 amount, in Nageli's view, to only one or two parts of the mass 

 of that of the female in the unfertilized egg cell or primordial 

 vesicle, and yet, if it contains an equal number of hereditary 

 units (Anlagen), then these must possess a hundred times more 

 "idioplastic power" than those of the egg. This purely empirical 

 mass theory of the mechanics of heredity preceded the chromo- 

 some explanation of the facts. 



With regard to the relative total amount of the idioplasm, 

 Nageli holds that it is probable that only a very small part is 

 to be designated as the idioplasm proper, while the remainder 

 must be regarded as trophoplasm or nutritive plasm. 



"The activity of the idioplasm makes itself everywhere evident where 

 an heritable process of growth or metamorphosis takes place. Its pres- 

 ence in these places may therefore be presumed. When, on the contrary, 

 there are places where neither growth nor metamorphosis can take place, 

 it is presumed that the cause may either be due to lack of the idioplasm 

 or partly to the fact that a proper mixture of idioplasm and tropho- 

 plasm is lacking." (p. 29.) 



The idioplasm is presumed to be in a continual state of migra- 

 tion toward the places of development, and the growth processes 

 are determined, first by the constitution of the idioplasm, secondly 

 by its quantity, and thirdly by the manner in which it is com- 

 mingled with the trophoplasm. (p. 29.) 



Nageli holds that either the idioplasm changes continually dur- 



