CAN THE SPERMATOZOON DEVELOP OUTSIDE 
THE EGG? 
JACQUES LOEB anp F. W. BANCROFT 
From the Rockefeller Institute, New York 
ELEVEN FIGURES 
I. INTRODUCTION 
The experiments on artificial parthenogenesis have shown that 
an egg which naturally cannot develop without sperm can be 
caused artificially to develop without being fertilized by sperm. 
It is natural to raise the question whether a spermatozo6n can 
be caused to develop into a larva without an egg. The experi- 
ments on merogony prove that a fragment of the egg deprived of 
a nucleus can develop into a larva if a spermatozo6n enters the 
ege; this shows that the egg nucleus is not necessary for the devel- 
opment. The phenomena of merogony do not yet prove that 
the spermatozo6n alone can give rise to an embryo. There are 
several reasons for doubting this possibility. In the first place 
we have reason to assume that the protoplasm of the egg is the 
embryo itself. If this be correct we can understand that the 
spermatozo6n might be able to transmit a number of characters 
to the offspring, without possessing the possibility of becoming 
an embryo or creating one outside of an egg. | 
In the second place it is possible that only the protoplasm con- 
tains the apparatus necessary for nuclear and cellular division and 
that a spermatozo6n is not able to create this apparatus. In the 
third place it is possible that the egg protoplasm of each species 
contains nutritive material and enzymes of so specific a character 
that it is not likely that we are able to imitate it in the near future. 
The attempt at causing the spermatozoén to develop without an 
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