ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 689 
results were actually due to the substances extracted from 
the spermatozoon. But his experiments are certainly in the 
right direction. 
The idea that the spermatozoon and the substances which 
cause parthenogenesis act only catalytically, has a great 
bearing upon the theory of life phenomena. It means that 
if we accelerate the processes of cell-division in the mature 
egg (by specific catalyzers) the egg can live; but if these 
processes occur too slowly at the ordinary temperature (as is 
the case in the unfertilized egg in normal sea-water), the 
egg dies. The introduction of the catalytic substances which 
accelerate the processes of development saves the life of the 
egg. This may be made intelligible on the following 
assumption. Two kinds of processes are going on in the 
mature egg after it has left the ovary. The one leads to the 
formation of substances which kill the egg; the other leads 
to the formation of substances which allow growth and cell- 
division, and are not poisonous. We may use as an illustra- 
tion Pasteur’s well-known experiments on the behavior of 
yeast cells in the presence and absence of atmospheric 
oxygen. In the presence of oxygen the yeast cells multiply 
on a sugar solution, while the zymase effect is comparatively 
small. In the absence of oxygen the multiplication of cells 
is limited or may stop, while the zymase effect becomes more 
prominent. The products of alcoholic fermentation are 
comparatively harmless for the yeast cell, and for this reason 
an increase in the fermentative activity of the cell does not 
cause the death of the yeast. I imagine that matters are 
similar in the mature egg cell after it has left the ovary, 
with this difference, perhaps, that the substances formed (by 
fermentation?) in the egg cell are more poisonous for the 
egg than the alcohol and the other products of fermentation 
are for the yeast. The process that causes the death of the 
egg cell and the one that causes cell-division are at least 
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