460 OSCAR RIDDLE 
posed entirely of white yolk—is much poorer in fat than is yellow , 
yolk. Since fat is the only food that can carry Sudan this is 
another reason for the failure of Sudan to appear in them. The 
Sudan method is therefore not available for the determination 
of the rate of growth in these eggs. 
One bit of evidence of another sort concerning this rate of 
growth was obtained and may be recorded. In fig. 3, pl. 2, is 
shown the striated appearance which the peripheral white yolk 
of one of the small eggs showed after having lain in a quantity of 
Mann’s formalin-aleohol mixture for a few weeks. Here the note- 
worthy facts are, that a striation exists, and that the lamellae 
are not thicker than 0.25 mm. Whether these lamellae are made 
up of still smaller strata which really represent days of growth 
I am quite unable to say. I doubt somewhat that the radius of 
these small eggs is increased by as much as 0.25 mm. in twenty- 
four hours; anyway these strata offer some evidence—in the 
light of what we know of succeeding yolk strata—that these 
small eggs do not grow faster than 0.25 mm. per day. 
One must ask what is the meaning of the extraordinary differ- 
ence in growth-rate of eggs under, and over, 6.0 mm. in dia- 
meter? What old mechanism is inhibited or what new one 
brought into action, that accounts for this procession of cells— 
each with months of slow and constant growth behind it—coming 
to a point from which each jumps in a day from its accustomed 
rate of increase, to a rate that is probably from eight to twenty 
times higher? Do the follicular cells now become more permea- 
able than formerly to the ingredients of yolk? Is the increased 
vascularity of the follicular envelopes, that certainly occurs at 
this time, a cause or a result of the new activity? To these ques- 
tions there comes no answer. But to us there are few events in the 
history of the primary oécyte of the fowl more interesting than 
this one. All the more interesting it is, too, because of its glar- 
ing apparent teleology. Here is an ovum within five to eight 
days of extrusion? and containing less than the hundredth part 
2Tt is true, however, that if the -yolk grow less rapidly than normally the egg 
remains longer in the follicle; showing that the time of ovulation is not controlled 
by heredity but is governed quite completely by conditions. 
