68 On the Reproduction and Embryogeny of the Aphides. 
above which they rise miore or less. The whole mass of these 
organs, the green colour of which being often very intense 1m- 
mediately catches the eye, is composed of large oval or poly- 
hedric cells, the characters of which I shall describe further on, 
im speaking of the formation of the seminal corpuscles. A very 
delicate envelope extends itself round each of them, and is con- 
tinued to the posterior part in an attenuated process, which 
loses itself upon the sides of the rectum, and probably represents 
an excretory duct. As the neck of the seminal vesicle may 
likewise be followed into this region, it is probably there that 
the union of these ducts with the spermatic reservoir is effected. 
As to the seminal vesicle, it is formed by a sac of considerable 
size situated on the median line above the intestine, with its 
fundus sometimes advancing nearly to the middle of the body. 
Its wall is formed by a simple structureless membrane, a true 
cell-membrane, of such delicacy and transparency that m most 
cases its presence is betrayed only by the seminal corpuscles and 
coloured granulations composing its contents—which explains 
how it has remained undetected by all observers. The seminal 
vesicle terminates by a very slender duct, which represents its 
neck, and which I have been able to trace to the point of union 
of the two ovarian tubes, where it is probably inserted. 
It remains for me, im conclusion, to say a few words about 
- the spermatic corpuscles and their formation. This commences 
very early; for all the embryos of the viviparous dphides at the 
moment of their birth contain new generations in course of 
development. Still more, it is not rare to find the spermatic 
reservoir, to the early formation of which I have adverted above, 
already filled with seminal corpuscles before there is any trace of 
an embryo in the ovum. These corpuscles are formed, as I have 
already stated, in the large coloured cells which constitute the 
mass of the two organs situated in the vicinity of the ovaries. 
At the moment of their appearance these cells contained only a 
homogeneous and colourless substance ; but as they enlarge they 
become penetrated by fine granules, which give them the green 
or yellowish-green colour presented by them im most Aphides ; 
at the same time their contents become converted into a multi- 
tude of little daughter cells, furnished with a membrane and a 
nucleus: these are the cells of development of the spermatic 
elements. They are, in fact, soon replaced by innumerable 
small dark corpuscles of 0°001—0:002 millim. in diameter, which, 
under a strong power, appear like minute Amebe; but their 
form does not change under the microscope. The large mother 
cells have then lost their transparency and their green colour, 
and become opaque and brownish ; they are easily disintegrated, 
breaking up into a sort of powder after the destruction of their 
