RECENT DISCOVERIES IN INSECT EMBRYOGENY. 
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the ovarian chamber, the granular mass, together with its in- 
cluded nucleus, as corresponding with the ordinary germinal 
vesicle, filling one end of the chamber , and the remaining cells, 
together with their surrounding matter, as representing the 
formative cells of the yolk filling the other part of the chamber. 
In the course of subsequent development the lining cells of 
this envelope disappear, and a line, or layer, of granules is found 
in their place. The dark, granular mass, with its enclosed 
nucleus, is the reproductive body (germ egg, or pseud ovum), 
a germinal membrane being formed over the yolk before it fills 
the entire chamber. The formative cells of the yolk disappear 
also as the bulk of the yolk increases, but three or four cells 
remain at one end of the chamber, and these M. Mecznikoff, who 
assisted Leuckart in his researches, found to be not vitelline- 
cells, but so-called “polar cells,” which were finally traced in 
the young embryo as the rudiment of its germ stock. These 
polar cells being, therefore, the progeny, by endagimous multi- 
plication, of the original cells lining the chamber, may be 
supposed to possess the reproductive power, and to be capable of 
repeating the procreative process when the larvae containing 
them have attained to independent life. 
With the other naturalists, Leuckart considers this organic 
larval propagation as essentially identical with that of Aphis. 
The germ stock of Cecidomyia he regards as an analogue of the 
sexual glands, and its filament of connection with the Malpighian 
vessels as a rudimentary efferent duct. Their germ stock being a 
sexual apparatus (female only?) the germ ball ranks as an ova- 
rian chamber, and its contents constitute the reproductive 
body (germinal cell and yolk, with residual polar cells which 
belong to the new germ stock) a sexual apparatus of the larva. 
The viviparous larvation on this plan is not “ gemmiparous,” 
but true Parthenogenesis, i.e. the procreation of germs or pseud 
ova in an organ of female character, unaccompanied by any 
fertilising element. None of our authors appear to have ob- 
served anything resembling the combination of germ and sperm 
cells, described by Balbiani as existing in the Aphis germ stock. 
The description given by the latter is, however, so enigmatical 
as to demand further corroboration. 
Leuckart objects to the use of the term ovum, though mor- 
phologically undistinguishable in the maturely developed germ 
chamber, because the larva is an immature animal, and sexless. 
The word “ pseud ovum” he admits as meeting the physiological 
definition of power possessed by the germ, but remarks that the 
“ alternate generation,” in this instance, differs from the usual 
form, because the sexual individuals which close the cycle of 
reproduction undergo further metamorphosis before they attain 
to maturity. 
