EECENT DISCOVERIES IN INSECT EMBRYO GEN Y. 
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the two ovaries. The most mature are collected at the posterior 
margin of the ovary, and their detachment occurs at intervals 
corresponding with the period of maturity of each “ pseud ovum.” 
After quitting, or even whilst within the “ ovary,” the yolk be- 
gins to form, first as fine opaque granules, scattered amongst 
the primitive cellules at one end (or pole), soon after which fatty 
particles with strongly marked outlines appear, and the ovum 
acquires an ovoid shape. The further development takes place 
after the ovum has left the ovary, and consists simply in an 
increase of yolk elements, which gradually fill the whole egg, 
and conceal from the observer what is taking place with the 
granules and primitive cellules. The ova, when let loose in the 
abdominal cavity, collect together at the posterior segments of 
the parent body, but, as the embryos grow, they reach by de- 
grees the middle and anterior segments. When they have 
attained their full development they escape, first, from their 
embryonal envelopes, and then rupture the skin of the parent 
larva, to enter life upon their own account. 
In the fully developed ovum the first changes observed are 
the formation, 1st, of a blastodermic layer on the surface of the 
yolk, and 2nd, of a layer of viscid matter, which soon gives 
place to a sphere composed of a regular layer of small clear 
cells. This, also, soon disappears. The form of the ovum has, 
meanwhile, undergone a change by the swelling of the ventral 
side. The embryo is developed from a clear, finely granulated 
mass, seen at the surface of the yolk. As it grows, the yolk 
disappears, but a part remains heaped up at the back of the 
embryo, and is afterwards transformed into fatty tissue. 
Thus all observers agree in representing the yolk of the ori- 
ginal insect egg as not wholly expended in the evolution of the 
first larva. But Ganine and Pagenstecher oppose the statements 
of Wagner and Meinert, that the fatty matter possesses the 
formative property attributed to it by them. 
5. We now come to the observations of Leuckart, for the 
full account of which we refer our readers to the translation by 
Mr. Dallas, published in the March number of the Magazine of 
Natural History (of the year 1866). The larvae examined by 
Leuckart were found under the bark of a dead apple tree, and 
belong to the species Oligarces (determined by Meinert). The 
origin of the free germs was traced (as by Ganine) to two small 
bodies (primitive germ stock), situated immediately under the 
skin of the eleventh segment of the larval body, and fixed by 
suspensory ligaments to the Malpighian vessels. 
These germ masses consist of a number of clear cells, each of 
which contains several vesicular nuclei. The cells lie in a 
granular protoplasm, the whole being enclosed within a fine 
membranous investment (the (i ovarial sac ” of Ganine). 
