ME. LUBBOCK ON THE OVA AND PSEUDOVA OE INSECTS. 
349 
Professor Stein, indeed, appears to consider that the vitelligenous cell is homologous 
with the germinal vesicle, and that the yelk is deposited round it without being enclosed 
at first in any distinct membrane. 
In the Diptera (Plate XVII. fig. 8, and Plate XVI. fig. 9) and the Hemiptera (Plate 
XVII. fig. 7) it is, I think, evident that the germinal vesicle corresponds to the nucleus 
of the vitelhgenous cell, and that the yelk-mass is in the early stages of egg-formation 
enclosed in a membranous envelope or cell, homologous with the cell-wall of the vitel- 
ligenous cell, and like it destined soon to be absorbed, but which in the mean time I pro- 
pose to call the egg-cell ; and even in the Lepidoptera, Hymenoptera, Geodephaga, and 
Neuroptera, though the matter is not quite so clear, any one who examines carefully 
the upper end of the egg-tubes will, I think, come to the same conclusion. 
Our knowledge of the modes of egg-formation in the Insecta is perhaps hardly yet 
sutficient to enable us to generalize with much confidence ; the following Table exhibits, 
however, the present state of our information on the subject ; and though many of the 
aberrant forms, as for instance Thrips and the Str^siptera, are not included, and it is 
therefore very incomplete, yet it will probably be found correct as far as it goes. The 
only two cases in which any families differ greatly, as regards the vitelligenous cells, 
from the remainder of the order to which they belong, are the Geodephaga and 
Hydradephaga from the remainder of the Coleoptera, and the Libellulina from the 
Neuroptera. 
d 
o 
■3 
be 
be 
s. a 
- a 
r 
El . 
O to 
•SP" 1 
Contained in a terminal chamber 
Absent 
One to each egg . 
Egg-chamber 
( Not constricted 
Constricted in the middle 1 
Coleoptera (generally). 
Homoptera. 
Heteroptera. 
Orthoptera. 
Pulex. 
Libellulina. 
Porfieula. 
Diptera. 
Lepidoptera. 
Hymenoptera. 
Geodephaga and Hydi-adephaga. 
Neuroptera (except Libellidina). 
In thus dividing the Insecta into two sections, according to whether or no each egg- 
germ carries with it a group of vitelligenous cells, we get a classification which is far 
from natuial, inasmuch as it separates the Libellulina from the rest of the Neuroptera, 
Pulex from the Diptera, and the two first sections of the Coleoptera from the remainder 
of that order. 
It is rather difficult to decide in which group the genus Porfieula (Earwig) ought to 
be placed, since each egg appears to consist of an egg-cell and one vitelligenous cell only. 
The second section, containing the insects which possess groups of vitelligenous cells 
forming a part of each egg-germ, combines most of the insects in which the power of 
flight is largely developed; but the Libellulina, which are pre-eminent in this respect, 
belong to the other series. 
The development of the prothorax appears to have some curious connexion with the 
presence of alternate groups of vitelligenous cells. Lacordaire* says, “ Si le pro thorax 
* Introduction a Entomologie, p. 326. 
3 A 
VDCCCLIX. 
