352 
HARRY R. ROSEN 
obtained a test for sugar. From this he concludes that the Cynipid 
larvae excrete an enzyme capable of changing starch to sugar. He 
states that at present there is a tendency to ascribe the stimulating 
agent in gall production to enzymatic action and he holds that this is a 
safe working hypothesis. He is careful to point out that only in the 
Cynipidae, referring to his own diastatic experiments, do we have 
experimental evidence for this. Magnus (i8) says, not only the 
larvae of the Cynipidae give off diastatic and proteolytic enzymes, 
but larvae of the Diptera do the same thing. He describes an ex- 
periment in which larvae of Dasyneura (Perrisia) terminalis were 
placed on a starch-gelatin medium and remained alive for a long time. 
After twenty-four hours, the starch around them had been dissolved 
in a ring, showing a diastatic action, and similarly the gelatin had been 
dissolved by proteolytic enzymes. However, he does not conclude 
from this experiment that gall production may be traced to these 
enzymes, and very critically he says: "Erscheint also auch immerhin 
die Mitwirkung der vom Gallentier ausgeschiedenen proteolytischen 
Enzyme bei der Gallenbildung moglich, ist hierfiir bisher kein Beweis 
erbracht, vielmehr gaben alle Versuche, mit proteolytischen Enzymen 
die Pflanzengewebe in andere Entwicklungsbahnen zu lenken, negative 
Resultate." 
Performing experiments along the lines described above, I ex- 
tracted hundreds of Phylloxera nymphs from galls and placed them on 
a starch solution. I obtained sugar tests in a number of such experi 
ments, while checks gave no tests. I am not sure, however, that I did 
not introduce wild yeasts or other micro-organisms along with the 
nymphs. However that may be, when I sprayed young vine leaves 
with a fine spray of a watery solution in which the nymphs had been 
deposited, my results were negative. Injections of this solution into 
the leaves with fine glass tubes all gave negative results. Since only 
a small number of injections were tried, the results may not be con- 
clusive. 
Magnus (i8), who has given us an excellent summary of the 
theories concerning the etiology of gall formation, concludes that the 
stimuli are not enzymatic as Beyerinck, Cosens, Molliard and others 
believe, or specific poisons, chemomorphs, as Kiister and others 
maintain, but substances which inhibit the action of enzymes, sub- 
stances which may be likened to the anti-enzymes of Czapek, anti- 
bodies of serum biologists, or hormones as described by Armstrong. 
