256 QUARTERLY CHRONICLE. 
That of Wagener is the Miastor, that of.Pagenstecher and 
Leuckart is Oligarces. 
In Miastor, the cells which become germs form part of the 
adipose tissue ; but in Oligarces they are a little separated from 
it, though they do not form an ovary properly speaking, for 
all the cells develope into eggs and larve, and none serve to 
form the stroma, or envelopes of the eggs, nor any analogous 
functions. M. Meinert explains the peculiarities of the 
Cecidomyia larvze by the following general views :—-The egg is 
composed either of a single cell, the “‘ germinative cell,” or of 
the germinative cell accompanied byothers—“ vitelline cells,” 
or their secretion the “vitelline mass.’”? The mammalian 
egg, and that of most inferior animals, belongs to the first 
category. That of other animals, and especially that of 
birds, belongs to the second, and that of most insects 
to the third sort. The single “ germinative cell” of 
which the nucleus is the “ germinal vesicle” is subject to the 
vitelline segmentation so much discussed. The “ vitelline 
cells” and the “ vitelline mass” are never broken up, but 
pass without any form of development to the nutritive vitellus. 
The germinative cell divides by “vitelline segmentation ” 
(or, as one ought by rights to call it, “segmentation of the 
germinative cell”) into minute cells (embryonic cells). One 
part of these embryonic cells, which are not absorbed by the 
formation of the embryo, furnish the material for the new 
ovaries and testicles ; and generally some of the cells form a 
stroma which separates and encloses a more or less consider- 
able quantity of other cells. The non-separated cells which 
remain form, among the insects, what one calls “ the adipose 
tissue.” Another element, the sperm, is necessary among 
most animals in order that the egg, or rather the germinative 
cell of the egg, may be able to develope ; but this stimulus is 
not always necessary among a large number of inferior ani- 
mals. The development-of the egg does not depend at all 
upon 2 certain more or less advanced point of development of 
the maternal animal, or of its ovary; for the maternal 
animal attains sometimes a complete development, even 
with the external and internal genital marks (partheno- 
genesis, the Bee); sometimes it advances only to the larval 
condition without genital marks, and this may repeat itself 
through several generations—in some cases under the same 
larval form (our Cecidomyia), sometimes under a diverse 
exterior (alternating generation, or rather metagenesis, 
Trematodes). M. Meinert does not at all admit that there is 
a marked limit between parthenogenesis and metagenesis, 
and that one can, for example, explain in two ways the mode of 
