ME. LUBBOCK ON THE OVA AND PSEUDOVA OE INSECTS. 
347 
culties. Each, egg-tube contains generally very few egg-germs, though in a small species 
belonging to the Syf^hidce^ and 1 believe to the genus Cheilosid^ there were as many as 
nine. In Melophagus ovinus Leuckaet has figured three, and I have found the same 
number in Musca and Eristalis tenax. In Tipula and Culex I found only one egg-germ 
besides the terminal chamber, which is present throughout this order as in the Co- 
leoptera. 
In the Hemiptera the egg-germs are few in number, and each egg-tube has a large 
terminal chamber. 
In the Homoptera but few species have been examined. They appear, however, to 
agree with the Hemiptera in having few egg-germs, and a terminal chamber containing 
vitelligenous cells. In Coccus hesperidwn and C. persicce I found only one egg-germ, in 
Aphrophora spumaria three ; and Letdig and Huxley * have figured five in an Aphis f . 
Histology. 
The egg-tubes consist of two membranes. I did not, indeed, succeed in seeing the 
outer muscular one clearly in every species I examined, and in some insects all the 
egg-tubes are enveloped by one common covering; but in most instances the outer 
membrane was distinctly visible between each two egg-chambers, where, unlike the 
inner membrane, it is not contracted, but retains nearly the same diameter, only 
tapering gradually from the most matm^e egg-germ up to the youngest. It is figured 
in Plate XVI. figs. 3 and 9, and Plate XVII. fig. 7. 
On the inner side of the internal membrane lie a number of cells. These form in 
most parts a continuous layer ; but in those insects which have between each of the egg- 
germs a small group of the remarkable vitelligenous cells, presently to be described, 
the epithelial cells at these parts of the egg-tube are scattered more sparingly, and are 
less distinctly visible. These epithelial cells take probably an active part in the secre- 
tion of the yelk, and subsequently in that of the chorion. 
Between each of the egg-germs in Lepidoptera, Hymenoptera, Geodephaga, Hydra- 
dephaga, and Neuroptera (except the Libellulina), is situated a group of cells, which 
increase in size from the anterior to the posterior end of the egg-tube. 
These cells, which, adopting the convenient name proposed by Professor Huxley, I 
propose to call the vitelligenous cells, were first noticed by HeroldJ, who however 
describes them as rings, and offers no opinion on their homologies or function. Steix, 
in his excellent work to which I have already had occasion to allude, gives a faithful 
description of these cells, and expresses a decided opinion that they secrete yelk-matter. 
Hermann Meyer § also has described these bodies in the egg- tube of Saturnia Carpini', 
but he considers them abortive ova ; an opinion, which, although adopted by Dr. Allen 
Thomson II, appears to me quite untenable. 
* Httxlex, 1. c. pi. 40. fig. 1. f Zeitsclirift fur "WissenscliaftlicLe Zoologie, 1849, pi. 5. 
J De G'eneratione Insectorum in Ovo. § Zeitsclirift fiir Wissenschaftliclie Zoologie, 1849. 
11 Article ‘ Ovum,’ p. 113, Todd’s Cyclopaedia. 
