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POPULAR SCIENCE REVIEW. 
After a time, these clear cells are found to contain a number 
of small cells, derived from the vesicular nuclei. By successive- 
development each cell is gradually transformed into a “germ 
hall,” which, when detached from the primitive germ mass, 
consists of a membranous envelope, lined by an epithelial layer 
of cells (corresponding to the sphere of clear cells described and 
prepared by Pagenstecher), within which are a number of cells 
(the developed vesicular nuclei), themselves containing a fresh set 
of vesicular nuclei. Thus, the “ germ stock ” of Leuckart, from 
which his “ germ balls ” are derived, corresponds to the “ ovary” 
of Granine : the “ germ ball ” corresponds to the “ pseud ovum ” of 
Granine, and is found loose in the larval body. In the physio- 
logical interpretation of these parts, our authors diverge con- 
siderably. Leuckart dissents from the nomenclature of previous 
observers, denying that the “germ ball” is an embryonal 
portion of the fatty tissue (Wagner, Meinert), or an ovum 
(Pagenstecher), or even a “pseud ovum ” (Granine). He affirms 
that it is a germ chamber (an ovarian tube, in fact), and that it 
gives off a reproductive body (pseud ovum), in accordance w T ith 
the type of egg formation in insect ovaries generally. The egg 
chamber of insects is, however, not, as in the case of these 
larvae, free , but fixed, and usually forms the terminal portion of 
an ovarian tube. Leuckart maintains, nevertheless, that the 
“germ balls” are a true analogue of insect germ chambers, and 
compares them, in particular, with the germ chambers of Melo- 
phagus, which are so deeply constructed as to be only united by 
a thin cord, and therefore almost as independent as the Cecido- 
myia germ balls. This opinion is supported by Leuckart’^ 
account of the morphological changes, as observed by him, 
during the further development of the embryo inside the germ 
ball or chamber. 
As before described, the mature germ ball consists of an enve- 
loping cell lined membrane, the interior space being full of cells- 
derived from the transformed vesicular nuclei. These secondary 
cells contain nuclei also. After a short time each secondary 
cell becomes surrounded with granular plasm, which distends-, 
the germ ball at one end until it assumes a pyroform shape. 
The granular mass at the other end differentiates into a sub- 
stance which quickly transforms itself into a distinct mass, filling 
up more and more of this interior space, the germ ball becoming 
oval in shape. At one end (or, pole), there lies embedded in the 
granular plasm a regular nucleus (germ cell), which does not 
increase in volume equally with the mass around it. In 
Granine’s figures this granular mass is distinctly shown, but 
described as the yolk mass of the pseud ovum. Leuckart, how-* 
ever, comparing the whole with an insect germ chamber,, 
considers the envelope with its cell-lining as corresponding with 
