98 RANADA. 
is more or less rapid, according to the temperature of the 
atmosphere; and that I was enabled to retard or hasten it 
by regulating this circumstance. I therefore kept my re- 
servoir of eggs in a very cold situation, and occasionally 
brought a few of them into my drawing-room for the pur- 
pose of observation ; in which place, being in an elevated 
temperature, the developement became very rapid. As my 
object, therefore, was to ascertain positive facts, rather than 
the periods of the changes, which were dependent upon 
variable circumstances, I kept no register of the tempera- 
ture or of the periods; and I shall, in both these par- 
ticulars, give some of the statements of the accurate 
Rusconi. 
The embryo is found, in the first place, to consist of a 
small globular body, one side, or hemisphere, of which is of 
a dark brown colour, the other being much paler. In a 
very short period after the egg is deposited,—four hours, 
according to Rusconi,—a deep furrow across the dark hemi- 
sphere divides it into two equal parts, and this is soon 
afterwards crossed by another at right angles; a third and 
a fourth furrow are produced, and so on, until the whole 
surface of this side of the sphere is, as it were, granulated. 
This appearance, however, is but transitory, the surface 
soon becoming almost smooth. In the course of the second 
day, the sphere begins to elongate, and a groove, which 
had previously divided the upper part of it into two equal 
parts, begins to close up. The head becomes prominent, 
the tail begins to shew itself, the little hooks by which it 
subsequently lays hold of objects and supports itself, begin 
to appear. At this period the examination becomes more 
easy, and more interesting. At somewhat more than fifty 
hours in an elevated temperature, the head is very well 
marked, the tail somewhat elongated, and even the rudi- 
