ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 43 
spermatheca has thick walls continuous with those of the vagina ; 
but its dilated portion is thin, and has a yellowish colour. It con- 
tains a multitude of large filiform spermatozoa bent upon themselves, 
and is very tough and resisting. 
The colleterial glands (7) are subcylindrical, but are constricted 
inferiorly where they open close to the vulva. They consist of a 
delicate structureless coat lined by a thick layer of granular sub- 
stance, whose cellular composition is very indistinct in the fresh 
state, but becomes obvious on the addition of acetic acid. 
The interior of the gland contains a clear, viscid, strongly-refract- 
ing substance, apparently separated from the epithelial lining by a 
membranous layer. I am in doubt, however, whether this apparent 
membrane be anything more than the folded and wrinkled outer 
layer of the viscid matter. When the Affzs is suddenly placed in 
glycerine or subjected to slight pressure, a drop of the colleterial 
secretion not unfrequently exudes and manifests its viscidity by 
leaving a long trail. 
The fully-formed ovum (PI. XL. [Plate 5] fig. 1, IF) measures. 
about jj>th of an inch in length. It is oval, rather smaller anteriorly’, 
and of a deep green hue, in consequence of the colour of the 
yelk. The chorion is a tough transparent membrane, about gy55th 
of an inch thick, and presents no external sculpturing or internal 
structure. Internal to the chorion is a delicate vitelline membrane 
which immediately invests the yelk. It is, however, connected with 
the chorion posteriorly. When the egg is heated with caustic potass, 
the yelk is driven away from the sides (eventually dissolving), ancl 
with it the vitelline membrane on the sides and at the anterior part 
of the ovum; posteriorly, however, I always found it adherent. The 
yelk itself is very coarsely granular; so that there would be no 
chance of discovering the germinal vesicle, even if it existed. 
The recent observations of Leuckart and Meissner on the micro- 
pyle of the ovum in Insects naturally induced me to look for such a 
structure in the egg of Aphis. 
Leuckart, in his elaborate essay, clearly shows that the micropyle 
may be single or multiple, and may occur at either or both poles of 
the egg; but unfortunately he gives us less information respecting 
the ova of the Homopterous Hemiptera than regarding those of any 
other great group of Insecta. Cercopzs, in fact, is the only genus of 
this division in which he has observed the micropyle with certainty, 
and here there are two—one on each side of the anterior pole. 
The anterior extremity of the chorion in Apfhzs (Pl. XL. [Plate 5] 
fig. 4, B.) presents a small conical papilla, in which I have been unable 
