The Biology of the Roach 67 
Thus we see all of these 54 egg cases (exclusive of the 
last, which might safely be regarded as abnormal), hav- 
ing a period of incubation varying from 45 to 56 days. 
The egg cases, as each was deposited, were placed in 
Jelly glasses and kept in the third floor laboratory. It 
seems to me that, if temperature has anything to do with 
hatching, this should have accelerated their development, 
for it was much warmer in the attic in July than in the 
cellar where the eggs normally are laid. 
Emergence of the young from the egg case-—When 
first I witnessed the hatching of the roaches, I was much 
surprised to find that their emergence is very similar to 
that of the mantis, Stagmomantis carolina. The roach 
egg cases are the well-known purses, the upper edge of 
which shows a ridge or seam. By one of those miracles 
which make marvelous every type of birth, this purse or 
capsule is pressed open at this seam at the moment of 
the emergence of the young, and the inmates are all 
released at the same time, after which, the pressure 
relieved, the capsule again closes and appears outwardly 
exactly the same as before. If one examines a number of 
egg cases previous to hatching time, and presses the ends 
together with the fingers in an attempt to open this seam, 
he will find them so tightly sealed that the case will mash 
under the pressure before this ridge will open. At hatch- 
ing time, however, they will yield readily, and at the 
slightest pressure will open beautifully, revealing the 
two halves of the case, each with the row of about eight 
mummy-like organisms, perfectly white except the eye- 
spots, which are black, and all arranged in two precise 
rows, heads up. In about three minutes after opening 
the case, all will have struggled out, and they are at once 
extremely active. This reveals the fact that when the 
egg case is deposited it has no opening, and only at the 
