KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 253 
already quoted work, ‘Die Continuitaét des Keimplasmas,’ &c. 
According to Weismann, with whose views Nageli’s theory of 
“‘idioplasm” (144) agrees in its essential features, we must 
recognise as the basis of all organic cells—and therefore of all 
organic beings—two different kinds of living substance (plasma) 
which essentially make up the cell body and nucleus. The one 
substance is generative, formative, directive, and transmitting— 
the so-called ‘“‘Kernplasma” (corresponding essentially with 
Nageli’s “ idioplasma ’’), the other (‘‘ Ernahrungsplasma ”) acts 
as the formed, nourishing, assimilating, mechanical substance. 
The former—Kernplasma—we must, according to the recent 
publications above reported on, seek for in the nucleus; the 
other chiefly in the cell body. Weismann believes that the 
Kernplasma directs, as it were, the whole being of the cells, 
brings about its division and its elaboration to a given form, 
whereas the “ Ernihrungsplasma ” has to attend to the incep- 
tion of new material for the support and growth of the cell, 
and at the same time serves as muscle-plasma, nerve-plasma, 
&c., for mechanical and other functions. The Kernplasma 
must be regarded as the form-giving, the essentially vitalizing 
element in every cell. It is especially abundant in egg-cells, 
as is natural. By the successive divisions of the egg-cell it 
must evidently pass into every cell of the body to a certain 
extent, since it is constantly being increased by the activity of 
the second or nutritive constituent—the “ Ernahrungsplasma.” 
Weismann further believes that Kernplasma exhibits two modi- 
fications, herein adopting an idea first formulated by Nussbaum 
(146). The one, the fundamental form of Kernplasma, is only 
sexual in character,is concerned only in reproduction; it is found 
onlyin the reproductive cells; the second arises from the first, and 
is that which later on is concerned in the division, growth, and 
shaping of the various cells of the body, even of the reproduc- 
tive cells (i. e. the egg- and sperm-cells) ; it hasa histogenic 
nature, whereas the primary form of Kernplasma has a sexual 
character, the latter being the vehicle of hereditary phenomena, 
Now, if the egg- and sperm-cells have both kinds of Kern- 
plasma, the histogenic and the sexual,the question arises whether 
