242 Fertilisation and Hybridisation. 



way, that their daughter-nuclei will share alike in the 

 hereditary characters that are present. The lengthen- 

 ing of the nuclear threads at the close of division, their 

 so frequent ramification, and the seemingly irregular in- 

 tertwining of their parts, evidently indicates the possi- 

 bility of a domination of the cell-life by the bearers of 

 the inhei'itable qualities. These must impress their 

 character on the surrounding protoplasm either dynami- 

 cally or, as I have assumed in my Infra cellulare Pangen- 

 esis, through a giving out of material particles to the 

 surrounding protoplasm, and thus promote growth and 

 development, in the prescribed direction, into the specific 

 form of the species to which the organism belongs. 



This secretion of material chromatin particles from 

 the nuclei was recently demonstrated by Conklin in Crep- 

 idula.^ In this way considerable quantities of chromatin, 

 and therefore probably of pangens also, are transferred 

 into the somatic protoplasm. 



Thus we consider that the structure of the nuclear 

 threads is such that it not only makes possible, but regu- 

 lates and dominates the relations of the two pronuclei. 

 In an ordinary animal, or in a plant which is not a hybrid, 

 both pronuclei possess the same units, only with a some- 

 what unlike degree of development. We assume, there- 

 fore, that the cooperation comes about in such a way that 

 the individual units in the stretched threads lie in the 

 same numerical order. Then, when the threads are 

 closely appressed lengthwise, in pairs, we can imagine that 

 all the like units of the two pronuclei lie opposite each 

 other. And this is obviously the simplest assumption 

 for a mutual influence. 



^Strasburger failed to find any direct evidence of such a transfer 

 of particles in plants. Cf . the Translator's Preface, p. viii. Tr. 



