52 
[August, 
transverse diameter is not diminished (rather increased, perhaps) in 
the middle. Moreover, the grasping of the last half of the egg by the 
finger-like appendages (and I have seen the flexible shell strongly in- 
dented by their action) tends to force the contents towards the other 
extremity, and so diminish the size of the last laid, which is also the 
cephalic, end of the egg. These conditions are often persistent ; so 
that I believe it may be possible to tell by them which side of the egg 
looked ventrally, i. e ., towards the surface of attachment, when laid, 
and which end will contain the head of the future larva. 
AVhen fresh laid, and enveloped in the glutinous matter, the eggs 
are perfectly smooth, shining and opaque. The colour is a clear yolk- 
yellow, varying a good deal in depth of tint in different individuals. 
I had once two females laying in the same pot whose eggs I could 
very easily distinguish in this way. There are often red ticks or short 
hyphen-like lines scattered sparsely and without regularity over the 
surface, like the markings on birds’ eggs. I have seen a speck of this 
red matter on the glutinous substance extending between two eggs and 
not attached to either. 
The eggs should be kept in a moist atmosphere during incubation, 
which preserves them plump and free from indentations, and greatly 
facilitates the hatching-out of the larvae. I generally cut out the 
piece of dock with the eggs upon it, and put it into a plaster-of-paris 
tray covered by a pane of glass. The eggs may either be turned down 
in the natural position, or up towards the light ; in any case, the 
venter of the larva developes on the side that is uppermost , whether 
that be the free surface of the egg or the surface of attachment.* 
This result is the same when all the light and heat falling on the eggs 
is made to reach them only from beneath, as I have proved by keeping 
them over mirrors, while the upper surface was kept cool by evapora- 
tion. It seems to be an affair of gravitation, as in the avian and 
batrachian egg. As the mature larva escapes from the free surface of 
the shell with the back of the thorax first, in those eggs which have 
been kept in the reverse position, and in which the venter of the larva 
has developed next the free surface, the young larva is obliged to make 
a half revolution on its long axis within the shell, before it can burst 
the latter and escape out of it. It hoists itself round, bringing into 
view the abdominal spiracles in a spiral line and the four conspicuous 
warts on the dorsum, to be presently described as the ‘‘thoracic 
square.” 
* This statement is only absolute for eggs laid evenly on a horizontal surface, and kept in the 
tame position throughout incubation. Even then, individual exceptions will be met with, as in the 
still rarer case of the cephalic and caudal ends lying the contrary way.— J. A. 0. 
