1892.] Heredity and the Germ- Celis. 661 
paternal elements in each cell; do they lie side by side or are 
they fused ? 
1st. In plants De Vries* and others believe that all or by far 
the greater number of cells in the plant body contain the total 
hereditary characters of the species in a latent condition. 
Kölliker’ has fully discussed this question and called attention 
to Miiller’s early views that, in spite of the physiological divis- 
ion of labor producing the tissues, the properties of all the 
tissues can be derived from the nuclear substance of a single 
tissue, as proved by experiments upon the lower animals. 
Weismann, on the other hand, has held that the course of 
development is marked by a constant qualitative distribution 
of his germ-plasm or hereditary substance, so that, so far as 
nuclear content is concerned, there are three forms of cells: 1, 
with nucleoplasm ; 2, with nucleoplasm and germ-plasm; 3, 
with germ-plasm only. Kölliker opposes this idea and main- 
tains that the “ idioplasma” passes into all cells, in which it 
divides in course of development; step by step from the 
embryonic layers to the tissues, the constructive processes are 
under the direction of the nuclei containing this hereditary 
substance ; it remains in every nucleus for a long period unal- 
tered, in order to finally, here earlier, there later, impress its 
constructive forces. In certain elements, as in blood-corpus- 
cles, epidermal scales, etc., it disappears, as the last product of 
division. 
R. Hertwig takes a similar view; since embryonic and adult 
cell division is differential there must be a form of differentia- 
tion in the nucleus, but this does not consist in the total elim- 
ination of some qualities and survival of others, nor of a 
reduction in mass. The mass and the properties remain the 
same in every cell, the differentiation consists in the activity 
of certain elements in certain tissues. Thus we may say with 
De Vries, that different “ pangene ” may leave the nucleus and 
enter the cell in different tissues, or with Nägeli, that special 
“ micelle ” come into activity at certain points; in other words, 
*Hugo de Vries: Intracellulare Pangenesis. Jena, 1889. 
Die Bedeutung der Zellkerne fiir die Vorgänge der Vaalin. Zeit. f. wiss. Zodl., 
1885. And, Das Karyoplasma und die Vererbung, op. cit., 1886. 
