CONTROL OF ASYMMETRY IN HYDROIDES 931 
were obtained by Wilson (’03) and Emmel (’08) there was an addi- 
tional factor, difference in time of removal of the two chelae, in- 
jury of the nerves of the chelae or the removal of the walking leg 
or legs on the side of the former more slender chela (see Stockard 
’10, discussed below). 
Wilson has suggested that the reversal may be under nervous 
control and he made a study of it in Alpheus by cutting the nerves 
going to the chelae. His results, as he himself recognized, are, 
however, not conclusive, since other influences, such as disturbed 
blood-supply, are not eliminated. Wilson also suggests that the 
snapping chela may develop always on the side of the body which 
has the greater amount of material to start with and which there- 
fore has the greater body of nutrition directed to it. Stockard 
has tested this hypothesis as applied to the whole group of append- 
ages on the two sides, by removing the walking appendages on 
the side of the cutting chela in the case in which the snapping 
chela is removed. The operation leaves the greater mass of ap- 
pendage ‘material on the side of the chela removed. Neverthe- 
less, practically all of the Alphei showed reversal as in cases 
without removal of walking appendages. Variations of these 
experiments showed the same negative result. The removal 
or non-removal of other appendages on either side has no proved 
relation to the phenomena of reversal. It should however be 
said that Stockard’s experiments do not test the essential point 
of the hypothesis of difference in amount of material or effective 
mechanism for growth in the form of blood-supply, etc., between 
the stumps of the two chelae themselves. The walking legs may 
not be directly concerned in the difference of activities of the two 
sides at the first chela level and the hypothesis of difference of 
materials at the first chela level be unaffected thereby. Further- 
more, if there be a correlation between these different levels, is 
it proper to assume, as Stockard has done, that the smaller amount 
of nutritive activity will be on the side regenerating other append- 
ages. As a matter of fact, the opposite assumption is indicated 
by some experiments (Zeleny ’09), and Stockard’s experiments 
themselves, as far as they show any difference in results between 
the two cases, point in the same direction (Stockard ’10). 
JOURNAL OF MORPHOLOGY, VOL. 22, No. 4 
