Autonomy of the Pronuclei 229 



times for a longer period, and, in the best cases, during 

 almost the entire vegetative life, the double nature of the 

 nuclei can here be directly seen. What van Beneden con- 

 cluded from the incipient stages was here irrefutably 

 proven. 



The double nature of the nuclei was also demonstrated 

 more or less distinctly, and during a shorter or longer se- 

 ries of cell-divisions, in other cases, by other investiga- 

 tors. It was observed in Toxopnenstes by Fol, in Sire- 

 don by Kolliker, in Arteniia by Brauer, in Myzostoma by 

 Wheeler, in the Axolotl b}^ Bellonci. These and numerous 

 other observations now place the law quite beyond doubt. 

 The independence or autonomy of the pronuclei corre- 

 sponds everywhere with the mode of union of the visible 

 parental characters in the offspring. 



In the snail-genus Crepidiila, Conklin recently discov- 

 ered a case in which the double nature of the nuclei can 

 be demonstrated perhaps even more clearly and easily 

 than in the Cyclops. If the nuclei remain side by side all 

 through life, the question arises as to how they dominate 

 together the development of the child, the unfolding of 

 its characteristics. Here, too, the results of physiology 

 and of anatomy work beautifully together, and here, too, 

 Goethe's lines serve as a guide.' Certain peculiarities are 

 inherited from the father, others from the mother. One 

 individual inherits them in this, another in that mixture. 

 The inheritance therefore consists of separate qualities, 

 which may be united in various combinations in the off- 

 spring. We are taught the very same thing by hybrids, 

 especially in their progeny, and the rich floral splendor of 

 our horticultural plants shows us what an endless number 

 of combination-types have already been achieved with 

 comparatively few characteristics. 



