and Embryogeny of the Aphides. 65 
have in a very different manner in the sequel of the develop- 
ment: that which has given origin to the female elements dis- 
appears immediately afterwards, whilst the vesicle which has 
generated the male or spermatic elements, far from disappearing, 
continues its development, often becomes very large, and after 
forming connexions with the female generative apparatus, con- 
stitutes a reservoir for the fecundative corpuscles—becoming, in 
fact, a true seminal vesicle for this hermaphrodite apparatus. 
When the curious phenomena just described summarily have 
terminated, the embryonic development, properly so-called, has 
not yet commenced. We may, indeed, observe that the cells of the 
blastoderm have multiplied at the anterior pole so as to produce a 
very considerable thickening there; but this modification is not fol- 
lowed by the formation of any new part. This thicker layer, in 
fact, soon gradually diminishes, and is at last entirely effaced*. 
XIII.—On the Reproduction and Embryogeny of the Aphides. 
By M. Barsiani. (Second Note.)+ 
In the viviparous Aphides the blastoderm assists to a certain 
extent in the formation of the embryo, but its part is exclusively 
limited to the production of the laminz which complete the ce- 
phalic extremity in front. All the rest, on the contrary, results 
from an entirely new part superadded to the blastoderm. 
The first phenomenon which denotes the commencement of 
embryonic development is a budding forth of cells upon one of 
the halves of the circumference of the aperture (of which I have 
already indicated the purpose and mode of formation) at the 
posterior pole of the blastoderm. The result of this budding is 
the production of a cellular lamina, which gradually rises from 
the margin of the preceding aperture into the interior of the 
ovum, folding back against the inner wall of the blastoderm, 
which it appears in some degree to double for a certain extent. 
When arrived within a short distance of the anterior pole, it folds 
inwards, inversely to its former direction, as if to descend again 
towards the aperture which was its point of departure, but with- 
out passing, at least at this time, the middle of the ascending 
periods of embryonic development and even after birth, has been described 
sometimes as serving for the nutrition of the embryo ( pseudo-vitellus of 
Huxley), sometimes as a plastic mass destined for the formation of the 
vegetative organs (Leydig). 
* This transitory production of the blastoderm of the Aphides is pro- 
bably the analogue of the “ primitive cumulus ” described by Claparéde as 
preceding the formation of the embryonal rudiment in the ova of the 
Spiders. 
+ Translated from the ‘Comptes Rendus,’ June 11th, 1866, pp. 1285- 
1289 
Ann. & Mag. N. Hist. Ser. 3. Vol. xviii. 5 
