RELATION OF TEMPERATURE TO DEVELOPMENT OF THE EGGS. 137 
lem under discussion. That it serves to bring to view an important 
factor that had not been sufficiently considered is undoubtedly true; it 
also clearly indicates, so to speak, an inner law of the influence of heat. 
Eeferring the reader to our First Eeport for an explanation and illus- 
stration of the theory as given by Professor Abbe, we propose to discuss 
it briefly here. 
That there is a limiting temperature below which, if continuous, the 
eggs will not hatch must be admitted. Just what that limit is has not 
yet been accurately determined, though approximately reached by the 
experiments made by Mr. Riley in 1876-77. 
But in door experiments, although conducted with the utmost skill 
and precision, are likely to vary more or less, in their results, from what 
will be found to be true in the actual out-door bfe of the species ; still 
they form a good basis upon which to work, and serve as an excellent 
guide to the fact sought for. 
Professor Abbe assumes the following as a "working hypothesis:" 207 
that, at a uniform temperature of 50° Fahr. the eggs require 65 whole 
days, or 1,560 hours, to hatch. 
At a uniform temperature of 60°, they require 60 whole days, or 
1,410 hours, to hatch. 
At a uniform temperature of 70°, they require 55 whole days, or 1,320 
hours, to hatch. 
It is proper to call attention in this connection to note 94, on page 428 
of our First Eeport, but the object we now have in view does not re- 
quire any explanation of the difference there alluded to. 
That eggs have repeatedly hatched in some of the northern sections 
when the maximum temperature had not at any time during the spring 
exceeded 52° or 53°, and seldom rose to 50°, is evident from data 
obtained by the Commission. We may therefore safely assume that a 
temperature of 50° is not below the hatching point. We may also as- 
sume as borne out by the facts that eggs deposited early in the season 
will, as a rule, hatch out, under the same conditions, earlier the next 
spring than those deposited later. Mr. Stolley, of Hall County, Ne- 
braska, who is in the habit of observing and recording the dates of 
depositing and hatching, had already noticed this fact, and so informed 
us in 1877. Professor Whitman and others have also observed the same 
thing. It appears, therefore, that the process of forming the embryo 
•commences in the fall, and that the sum of the heat above a certain 
degree is a factor not to be overlooked ; and we may remark here, as 
indicated by what has been shown in this chapter, that the sum of the 
cold below a certain degree also appears to be an important factor in 
the problem. 
As Mr. Stolley gives us the exact date at which eggs were first de- 
posited in Hall County in 1877, let us try Professor Abbe's "working 
basis" and theory by an examination of this case. It is true we have 
no meteorological record for that immediate section, but as Omaha and 
First Eeport, page 428. 
