472 OSCAR RIDDLE 
a typical example—of the reversibility of lipase effecting speedy 
and rhythmic transformations. The example too, becomes of con- 
siderable zoological interest, since certainly nowhere else does this 
simple physiological principle have such a relation to interesting 
features of morphology as just here. For, not only does it in 
these cases often completely change the features of the egg-cell, 
but itresults ina condition (telolecithal) which later gives direction 
to a host of events of early development—cleavage, gastrulation, 
etc.—which proceed from the egg. 
When we have spoken above of proof of the synthelic and of the 
analytic action of lipase we mean, of course, proof that each of 
these reactions may predominate in the egg. The burden of our 
whole statement is that both sorts of reaction are going on 
simultaneously (since thereaction is a reversible one), but that the 
conditions in the egg are, as a matter of observed fact, shown to 
be such that during the growth period the synthetic reaction 
normally exceeds the analytic; and that during incubation the 
reverse is true. 
We say nothing in this connection of the origin and disintegra- 
tion of the proteins of the egg. This group does not furnish, at 
present, examples specially proved for conditions in the egg, as 
do the fats. The reversibility of proteolytic enzyme action has 
however been demonstrated. 
With yolk-forming enzymes (lipase, etc.) accelerating a series of 
reversible reactions in an egg-cell in which traces of yolk have been 
deposited, what are the factors which favor each side of the reac- 
tion, and thus induce either an increase in the amount of yolk, 
or a decrease in the traces that already exist? We believe that 
for the ovum of the fowl which we shall more specifically consider, 
some of the factors effective elsewhere may be ignored.‘ The daily 
temperature fluctuations, for example, are relatively slight, ete. 
There seems good reason to believe that the amount and pro- 
4 There are several other factors or conditions which possibly, even probably, 
play parts in the storage of facts, i. e., building of yolk, in the egg; most of 
these however are factors supplementary to those of distribution coefficient and 
enzyme reversibility; though some are not. Some such factors known to be 
effective in fat-storage elsewhere are: (1) quantity of lipase (Kastle and 
Loevenhart) ; (2) different species (?) of lipase (Hanriot); (3) alkalinity 
