PBESIDENTIAL ADDRESS — SECTION D. 185 



But it is to be specially uoticed that genii-cells and somatic 

 <3ells do not stand in fundamental antagonism in the vegetable 

 kingdom ; the evidence, in fact, leads us to the conclusion that 

 probably the germinal elements are present to a greater or less 

 extent in all the cells of the plant. As proof of this, de Vries 

 adduces specially the phenomena of galls. A gall which is 

 developed as a result of insect-action on a leaf always contains 

 -elements normally only found in the bark of the stem. And 

 -quite as cogent proof, it may be added, is afforded by such 

 plants as Begonia, in which a new plant containing all the 

 tissue elements may be developed from a part of a leaf. 



Now", as shown by the results arrived at by various investi- 

 gators of cell-structure, it is in the nucleus of the reproductive 

 cell that hereditary characters must be conveyed. Further, 

 from the fact that in the act of fertilisation only the nucleus 

 of the sperm-cell fuses with the nucleus of the egg, while yet the 

 whole of the paternal characters pass over, it is not only to be 

 concluded that the paternal characters are represented in the 

 male nucleus, but that after fertilisation germinal elements 

 pass out from the nucleus, and penetrate into other parts of the 

 ovum and its derivative cells, the component parts of which 

 show characters derived from both the male and female 

 germinal cells. Thus, though the nuclei are the bearers of the 

 hereditary characters, the latter pass out from the nuclei in 

 order to become manifested in the body of the cell. 



De Vries claims to account for all the known phenomena of 

 heredity by his hypothesis of intracellular pangenesis, which is 

 thus summarised by him : "I call pangenesis (apart from the 

 hypothesis of the transport of the germinal material through 

 the whole body) the view of Darwin that the individual heredi- 

 tary characters in the living substance of the cells are con- 

 nected with certain material particles or gemmules. These 

 particles bearing the hereditary characters I name pangenes. 

 Every hereditary character, however many species it may be 

 found to recur in, has its special kind of pangene. In every 

 organism there are many such kinds of pangenes collected 

 together, the more numerous the higher the organization. 



" I call intracellular pangenesis the hypothesis that the 

 entire living yrotoplasni is built up of pangenes. In the nucleus 

 are represented all kinds of pangenes of the individual in ques- 

 tion ; the rest of the protoplasm contains in each cell essentially 

 that kind only which should attain to functional activity in it." 



"The whole living protoplasm consists of such pangenes 

 which have passed out of the nucleus at various times, with 

 their progeny. It contains no other living substratum."* 



* Not having de Vries's work now at hand, I have been indebted in 

 the compilation of the above brief account to a paper by Bolcorn in the 

 " Biol. Centralbl." (1889). 



