254 W. WALDEYER. 
it is convenient that, at the moment of fertilization, they should 
still contain the two kinds? Weismann thinks that this ques- 
tion must be answered in the negative. It must be beneficial 
to the phenomenon of fertilization and development, if the 
originally sexual form of Kernplasm (the “ Keimplasma,” as 
Weismann calls it, in opposition to “histogenic Kernplasma’’) 
is alone present. And therefore the histogenic Kernplasma of 
the egg-cell is extruded as the first directive corpuscle. 
Even the case of eggs developing parthenogenetically is now 
intelligible, since we ought to find in them at least one 
directive corpuscle. 
As for the second directive corpuscle, Weismann came to 
the following conclusion :—When in a sexually developing egg 
the spermatozoon reaches the egg-cell, it brings of course its 
Keimplasma to the egg-cell. We will call the female Keim- 
plasma, which remains in the egg-cell of a supposed first genera- 
tion a, that of the approaching male cell is a, ; so the fertilized 
ege-cell hasa Keimplasma of acompositiona+a,. In this state 
the Keimplasma now passes over into the sexual cells (eggs and 
spermatozoa) of the offspring, which develop into the second 
generation. The same will happen for a sperm-cell of this 
generation ; which since it arises from other parents, has, we 
will suppose, a plasma-formula 6+4,. Now, if an egg with 
plasma a+qa, is fertilized by a spermatozoon 6+4,, the Keim- 
plasma of the third generation will have a composition of 
a+a,+b+6, We now take the fourth generation in which 
there comes to an egg with Keimplasma of value a+a,+6+6, 
a spermatozoon with the same grade of composition of Keim- 
plasma—i. e. with a formula c+¢,+d+d,. So that the egg- 
cells and sperm-cells arising from this fertilization have a Keim- 
plasma with a composition a+a,+6+4,+e+¢,+d+d,. And 
so it is easily shown that, assuming only the Biblical age of 
mankind, the egg- and sperm-cells of existing human beings 
must havea similar but immensely complicated composition of 
their Keimplasma. But still another reflection arises :—In each 
nucleus of a certain size, evidently only a certain amount 
of Keimplasma can be present. If, therefore, the Keim- 
