10 MONTGOMERY — CELLULAR BASIS OF HEREDITY. [Jan. 15, 



their keen critical analysis of the experiments, that the chromatin 

 alone can be considered the bearer of the hereditary traits. 



From all these results it is concluded that the chromatin is the 

 seat of the hereditary growth energies.^ 



And from another point of view this is rendered probable. The 

 microchemical study of the cell has shown that the chromatin is 

 the most active substance concerned in cellular metabolism ; and 

 experimental work, particularly that of Verworn, shows that a cell 

 deprived of its nucleus, and hence of its chromatin, is unable to 

 build up new substances. The chromatin accordingly, as it is 

 transmitted from generation to generation, carries with it certain 

 definite metabolic energies characteristic of the species. And from 

 this view there is good reason to consider the idea of Delage (Z« 

 structure du protoplasma et les theories sur V Heredite, 1895) to 

 be in the main correct, namely, that the offspring is like the parent 

 because it has similar metabolic energies. 



V. 



There is another series of facts known about the behavior of the 

 chromatin, the hereditary substance, in the germ cells, and a few 

 of them will be touched upon. Oscar Hertwig showed, in 1875 

 {Beitrdge zur Kenntiiiss der Bildung, etc.^ des tierischen Eies), that 

 the fertilized Qgg cell contains two nuclei, one belonging to the egg 

 cell itself and one introduced by the spermatozoon. Then Van 

 Beneden (/. c.) demonstrated that the spermatozoon brings in just 



1 It has been argued by an English writer whose name escapes me, as does 

 the title and date of his paper, that the linin is the hereditary substance. 

 Active chromatin is never disassociated from linin, but there is always a sub- 

 stratum of linin in each chromosome, and in the rest stage the chromatin is 

 always supported upon linin strands. Hence it was argued that the linin is like- 

 wise equally distributed in cell division. This is a good point, but there is a 

 strong objection to it. When the daughter chromosomes separate, in the ana- 

 phase, the Hnin becomes pulled out between every two corresponding chromo- 

 somes as a connective fibre, and in the reconstruction of the daughter nuclei the 

 greater portion of such a fibre is not taken up again into the nuclei. And this 

 fact cannot be used in favor of the intracellular pangenesis theory of de Vries, 

 whereby pangenes are hypothetically supposed to wander out of the nucleus and 

 so determine the differentiation of the cleavage cells, for the connectire fibres 

 appear to behave alike in all cell divisions. Thus of the two constituents of 

 the chromosomes, at each cell division some of the linin becomes displaced into 

 the cytoplasm, but all the chromatin passes into the nucleus. 



