324 WHEELER. [Vot. IIT. 
1. Resting with the lateral faces perpendicular and crista 
uppermost. 
2. Resting on the crista with the tated faces perpendicular. 
3. Resting on the left lateral face. 
4. Resting perpendicularly on the anterior end. 
5. Resting perpendicularly on the posterior end. 
In all these cases the eggs developed normally, without the 
slightest indication of displacement in position or alteration of 
shape in the embryos; whether they were forced to develop 
with their heads pointing up or down. 
The development was slow in all of the above cases, but this 
was not due to the unnatural positions of the capsules, but 
rather to the low temperature produced by the evaporation of 
the water under the bell-jar. That this was the true cause was 
shown by capsules kept under the same bell-jar in the normal 
position, on the right side. Their development was likewise 
retarded. 
We may conclude from these few experiments that the force 
of gravitation has no perceptible effect on the development of 
the eggs of Aéatta, but that these highly differentiated eggs, 
utterly unable to revolve in their envelopes like the eggs of 
birds and frogs, have their constituents prearranged, and the 
paths of their nuclei predetermined with reference to the parts 
of the embryo. As the only difference between the mature 
ovarian and the oothecal egg is a difference in shape, we con- 
clude that the predetermination is effected before fecundation, 
and even before the formation of the first polar globule. 
There is nothing in the structure of the newly laid egg of 
Doryphora to prove that it possesses a dorso-ventral differentia- 
tion like the egg of Avatta; nor are my facts sufficient to war- 
rant the assertion that the ventral plate develops on the side 
opposite the point at which the polar globules arise. Still the 
possibility of such a condition is in nowise precluded, and the 
observation of Blochmann and myself on 4/atta probably apply 
to the Hexapoda in general. The spherical form of the Crusta- 
cean egg as opposed to the oval shape of the great majority of 
insect eggs, will be a great obstacle in the way of proving any 
similar conditions in this lower group. 
It can be proved, however, that we have as true an anteropos- 
terior differentiation in the eggs of Doryphora as in Blatta. 
