340 
Journal of Agricultural Research 
Vol. XXV, No. 8 
FERTILIZATION 
Prior to first maturation of the oocyte nucleus, the sperm is found in 
any part of the inseminated egg; but shortly afterward it assumes the 
appearance of a somewhat elongate or crescentic nuclear body (PI. 2, 
A-I). It is regularly found thereafter in the posterior half of the egg. 
After the second maturation the male nucleus becomes spherical, 
stains deeply, and measures 1.5 m in diameter (PI. 2, K-P). At the 
eleventh hour the male pronucleus expands until it measures 2 y in di¬ 
ameter. At about the twelfth hour the male and female pronuclei are 
found regularly close to each other (PI. 2, R-T) in the posterior part of 
the egg. Fusion of these two nuclei (PI. 2, U) is effected at about the 
sixteenth hour. The egg now contains a polar nucleus in the anterior 
region and a single cleavage nucleus located in the posterior region 
(PI. 2, W). 
ORIGIN OF THE PARANUCLEUS 
During the development of the embryos rounded or crescentic nuclear 
masses (PI. 3, A-F) are found in the nutritive membrane (trophamnion) 
which surrounds the germs and blastulas. These were termed paranu¬ 
clear masses by Marchal (3) in a species of Encyrtus that develops 
by polyembryony. Silvestri (9, jo, jj), Patterson (<?), and Leiby ( 2 ) 
have shown in other polyembryonic Hymenoptera that the paranuclear 
masses have their origin in the polar bodies. Paranuclear masses having 
a similar nutritive function are not confined to the polyembryonic Hy¬ 
menoptera; for they have also been demonstrated by Marchal (4) in the 
monembryonically developing species of Synopeas, Trichasis, and Platy- 
gaster ornatus . 
The two polar bodies developed in the course of maturation in Platy- 
gaster hiemalis also give rise to a polar nucleus or paranuclear mass. At 
the close of the eighth hour they lie close to each other in the anterior end 
of the egg (PI. 2, N), where they are recognized as compact, darkly 
staining masses of chromatin measuring approximately 0.7 n and 1.0 ji in 
diameter, respectively. 
The first polar body, unlike those in all other polyembryonic Hymen¬ 
optera previously described, does not divide during second maturation. 
Instead, the two polar bodies fuse to form a single polar nucleus (PI. 2, 
0-Q) at about the tenth hour. This behavior of the polar bodies differs 
from that shown by Silvestri (n), in Platygaster dryomyiae , in which he 
found that the first polar body divides, and that the anterior half of the 
divided first polar body forms one polar nucleus, while the posterior half 
of the first polar body and the second polar body fuse to form a second 
polar nucleus. 
Between the tenth and twelfth hours the polar nucleus elaborates until 
it fills most of the anterior region of the egg and measures about 4.5 n in 
diameter (PI. 2, R). It remains a single more or less spherical nucleus 
(PI. 2, S-V) until just before the division of the cleavage nucleus, when 
it divides amitotically to form two subequal paranuclear masses (PI. 
3 > A). 
differentiation of embryonic region and formation of 
TROPHAMNION 
About the twenty-fourth hour two regions are recognized in the egg, 
when the central part of its posterior half becomes distinctly differentiated 
