644 STUDIES IN GENERAL PHYSIOLOGY 
ever, the only light that can be thrown upon the nature of 
the process of fertilization must be expected from an analysis 
of the effects of a loss of water upon the egg. 
It seems as if the liquefaction of the nuclear membrane 
and other constituents of the nucleus were a prerequisite for 
cell-division. Norman showed that a certain increase in the 
concentration of the sea-water brings about a distribution of 
the chromosomes in the egg. Morgan’s observations agree 
with this. But as all these observations were made with 
solutions whose osmotic pressure was considerably higher 
than that of the solutions used in my experiments, new ob- 
servations will be required to decide this question. Hoppe- 
Seyler, in one of his papers, points out that a loss of water 
on the part of the protoplasm brings about a diminution 
in the processes of oxidation. We know that lack of 
oxygen can bring about the liquefaction of solid con- 
stituents. I add these remarks for those who enjoy the 
speculative side of biology. But at the best a theory can- 
not give us anything more than the facts it includes, and 
‘it is therefore clearly our task to supply the lacking ex- 
perimental data in this field of biology before we begin 
to theorize. 
7. I think we should try to discover first of all whether 
the process of development can be started by depriving the 
egg of water in a few forms only, or whether this is a gen- 
eral condition. I have thus far tried among the sea-urchins 
Arbacia and Strongylocentrotus franciscanus and purpuratus. 
Each of these forms is capable of osmotic parthenogenesis. 
I am confident that the same is true for all species of sea- 
urchins, although the optimal increase in the osmotic pressure 
of the surrounding solution may vary for different forms. 
But I consider it of more importance that with the same 
methods I have been able to produce artificial partheno- 
genesis in a starfish (Asterias Forbesii). By putting the 
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