ME. LUBBOCK ON THE OVA AND PSEUDOVA OP INSECTS. 
351 
Gryllus, Locusta, and Acheta, and probably prevails also through the Phasmidw* and 
Mantidce, which two latter families, however, I have as yet had no opportunity of exa- 
mining. It is, however, quite possible, if not probable, that we may find in them some 
approach to the peculiar type exhibited by the remarkable genus Forficula (Earwig). 
In the Libellulina the egg development is remarkably similar to that of the Ortho- 
ptera, with which it agrees in the absence of the large vitelligenous cells, and of any 
terminal germ-chamber. The egg-tubes are excessively numerous, and I have generally 
found from twelve to twenty eggs in each. 
The macula of AEschna (Dragon-fly) consisted apparently of several small vesicles, 
which gradually increased in size in unequal ratios, until at length one large one 
became pre-eminent. The end of each egg-tube terminates in a chord-like tube. 
In Pulex (Flea) also the type appears to be the same. There is here the same absence 
of the vitelligenous cells and of the terminal germ-chamber. If, however, a young spe- 
cimen be examined, fewer egg-chambers will be found ; and at the end of the egg-tube 
there will be a false, or rather perhaps a temporary germ-chamber, destined eventually 
to be entirely occupied by egg-germs, and to lose gradually its special character. In the 
most advanced tube I found fourteen egg-germs occupying the whole width of the bore, 
besides a great many others in less forward stages. 
The germinal vesicle is dark, large, circular, and very distinct. I could not see in it 
any macula ; but in two or three cases, shortly before its disappearance, it looked as if it 
was breaking up into a number of small ovate bodies. 
It is very remarkable, that in spite of the numerous affinities existing between Pulex 
and the Piptera (Gnats and Flies), the mode of egg-formation in these two groups is 
entirely different. 
In the Hemiptera (Plate XVII. fig. 7), the egg-tube terminates in a large terminal 
chamber full of round cells, each of which can apparently become an egg-cell or a vitel- 
ligenous cell. In this type, therefore, the vitelligenous cells, instead of being divided 
into small groups, one at the posterior end of each of the egg-cells, are all collected 
into a common germ-chamber at the end of the egg-tube. 
I was for some time in doubt whether the cells in this common germ-chamber did 
really contribute to the formation of the yelk. In Aphis, however, in which the same 
type of ovary exists. Professor Huxley f discovered, as before remarked, a duct or passage 
leading from the germ-chamber through the anterior, to the more developed egg- 
chambers. A similar structure exists in Nepa (Water Scorpion) (Plate XVII. fig. 7), 
and some other Hemiptera ; and as there can, I think, be no doubt that it is really a duct 
through which the yelk-substance descends to the growing egg, it follows that some at 
least of the cells in the terminal germ-chamber do really fulfil the office of vitelligenous 
cells. 
In the common Nepa cinerea I once found as many as five of these vitelliferous ducts 
(Plate XVI. fig. 10) in an egg-tube containing seven egg-germs, so that it seems probable 
* Mullee, Nova Acta Nat. Cur. xii. 2. t Loc. cit. 
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