350 ME. LUBBOCK ON THE OVA AND PSEUDOVA OP INSECTS. 
a acquis un developpement extraordinaire, et s est en quelque sorte separe du mesothorax 
et du metathorax, on aura le thorax d’un Coleoptere, d’un Dermaptere, d’un Orthoptere 
et d’un Hemiptere. Si au contraire le prothorax est reduit a des dimensions tres-exigues, 
et que le m^sothorax intimement uni au metathorax ait pris un accroissement enorme, 
on aura celui d’un Hymenoptere, d’un Lepidoptere et d’un Diptere.” And again, in 
page 332, after having described the prothorax of the Coleoptera, Deimaptera, Orthoptera 
and Hemiptera, he says, “ Avant de consid5rer le prothorax des memes ordres sous un 
point de vue plus en rapport avec ses usages dans la nomenclature, il est essentiel de 
connaitre les modifications qu’il subit chez les Hymenopteres, les Lepidopteres, les 
Dipteres et quelques Neuropteres.” 
The Diptera, H}mienoptera, and Lepidoptera, thus nearly allied to one another by 
the structure of the thorax, also agree very nearly in the type of egg-development. 
In the Libellulina also (Dragon-flies), the prothorax is rather large and distinct from 
the rest of the thorax. 
The Geodephaga and Hydradephaga, however, are subversive of this cuiious coinci- 
dence, which would otherwise have been as complete as that of the coexistence of rumi- 
nation and cloven feet; or the inward bending of the condyle of the lower jaw, with the 
other characters of the Marsupialia. 
In the Orthoptera we find, on the whole, perhaps the simplest tjpe of egg-foimation 
which occurs in insects, the large vitelligenous cells being entirely absent, and their 
functions probably monopolized, instead of being only shared, by the small cells which 
line the membrane of the egg-tube. 
The number of egg-chambers in each egg-tube is generally numerous; in BJatta 
orientalis (Plate XVI. fig. 1) amounting to as many as twenty-three. In each of the egg- 
chambers the germinal vesicle is easily visible, lying nearly in the centie, and possessing 
a distinct macula. The germinal vesicle in Blatta orientalis (Cocla’oach) is rounded in 
the upper chambers, but in the lower ones is somewhat elongated transversely. The 
macula germinativa is small, round and simple, as is the case in Acheta. In a species of 
Locusta (Grasshopper) I found the germinal vesicle in the lower chambers, hing near 
the posterior end of the egg ; in other words, near the end which is turned towards the 
vulva. In Acheta domestica (Cricket), as in Blatta, the macula is a small romid vesicle 
in diameter in the lowest egg-chamber in which it is visible, and gradually dimi- 
nishing to 6 ^ 0 - lower chambers a minute nucleolus can be seen in it, which is 
about 40 ^ in diameter. I never found in Acheta any other vesicular structm-es in the 
germinal vesicle, but there is in the anterioi’ or smallest geiminal esicles, a conspicuous, 
dark, granular mass, which both Wagnee and Stein* seem to have taken for the true 
macula. This dark granular mass is single in about the first four egg-chambers, and 
often conceals the true macula ; it then gradually breaks up, and in the three or four 
most mature egg-germs is reduced to a cloudy mass of very fine granules. 
The type of egg-formation which is represented in Plate XVI. fig. 1, is found in Blatta, 
* Loc, cit. p. 49. 
