No. 2.] BLATTA AND DORYPHORA. 301 
this has not been observed in any other arthropod eggs hereto- 
fore described, excepting Musca (Bruce, 7). The pear-shaped 
dilatation of the chorion is directly over the head of the future 
embryo and hatching insect, and is possibly more easily rup- 
tured or dissolved than the surrounding chorion. 
Of 40 capsules examined for the purpose of noting which 
ovary sent out the first and which the last egg, 32 com- 
menced with the right egg (from the left ovary) and closed 
with the left egg (from the right ovary), six capsules commenced 
and closed with the right, and one commenced and closed with 
the left egg. Evidently the 32 were normal; in the insects 
which deposited the six, one of the ovarioles was probably 
either atrophied or wanting, though the perfectly alternate 
arrangement of the eggs in the capsule was in nowise inter- 
rupted on this account. The two remaining egg-capsules were 
small and abnormal. 
The number of eggs in a capsule, far from being constant in 
Periplaneta orientalis, is even more fluctuating in Blatta ger- 
manica. In 34 capsules counted the average number was about 
40, the least number 28, and the greatest 58. The number 
varies in different localities and is doubtless dependent on the 
food of the female insect. In several capsules obtained where 
amylaceous food was abundant the average was much higher 
than in a much greater number of capsules obtained from a 
place where fatty food was the only diet. 
The above description of the oviposition of Blatta germanica 
probably applies to most species of the Alattide. But this 
species differs from Perzplaneta and probably many other forms, 
in rotating the capsule, a process now to be described. As 
soon as the last egg has passed the vagina and been placed in 
the capsule, the latter begins to rotate on its longitudinal axis, 
till the crista has described one-fourth of a cylinder to the right. 
The capsule is now in a horizontal position having its greater 
transverse diameter parallel with the corresponding transverse 
diameter of the insect’s body. The abdomen contracts during 
oviposition, and its end comes to lie anterior to the tips of the 
wings, so that the broad ends of the latter hide and protect the 
protruding end of the capsule. The rotation requires about a 
day. In one case a female kept the capsule in a vertical position 
for two weeks, apparently from some inability to revolve it. In 
