Internal Factors of Sex Determination 421 
also we lack the clew that tells us in what condition the charac- 
ters are represented in the egg. 
The Physiological Conception of Sex Determination 
From this point of view we may consider the protoplasm as 
a substance capable of assuming one or another condition that 
is determined, for the time being, by the environment or by inter- 
nal conditions. We may suppose that the same end-result 
(sex, for example) may be determined by different factors in 
different species. JI mean that while in certain species one kind 
of factor commonly determines the result, in other species other 
factors may determine which of the possible alternatives is fol- 
lowed. The protoplasm may be looked upon as being in a con- 
dition of equilibrium as far as the adoption of either alternative 
is concerned, and which one is followed is determined by those 
conditions that bring to the front the one or the other possible 
state. 
An illustration may make this clearer. In certain male crabs 
the right and left chele are different in structure. In some 
species it is always the right-hand claw that is the larger, in 
others the left, while in some cases either the right or the left is 
the larger. It has been shown by Przibram for some species of 
the latter class that if the large chela is removed the small one 
becomes the larger at the next molt, and in place of the large one 
removed a small one regenerates in its place. Both claws have 
potentially the same possibilities of becoming large or small. 
External or internal conditions determine which kind of develop- 
ment takes place; but the selection once made, the differentiation 
proceeds strictly along one line. 
Now in this case we might assume that when the big claw of one 
side is removed, all the preformed elements (primoidia) of the 
big claw contained in all the cells of the small claw begin to 
develop and dominate and replace the already-controlling-small- 
claw-forming elements. That is the morphological way of ex- 
plaining the result. On the other hand, the other — the physio- 
logical — idea makes use of no such mechanism, but assumes 
