PLATE 3 
Plaiygaster hiemalis 
A. Like X on Plate 2, but the egg has increased in size and is henceforth known as 
the parasite body. During the one to two day interval the polar nucleus divides to 
form two paranuclear masses. The polar region and the part of the parasite body 
surrounding the embryonic region is known as the trophamnion. X2,2oo. 
B. —Section of a parasite body between two and three days after opposition. The 
segmentation nucleus divides to form two embryonic nuclei. X2,2ob. 
C. —Parasite body about 3 days old, showing two embryonic nuclei in the embryonic 
region. One of the paranuclear masses begins to migrate in the trophamnion toward 
the embryonic region. X2,2oo. 
D. —Parasite body four or five days after oviposition. The two embryonic nuclei 
of the previous stage have divided to form four embryonic nuclei. X2,2oo. 
E. —Section of an aborted and degenerating egg. ><2,200. 
F. —Composite drawing of two sections of a 6-day-old parasite body showing four 
embryonic nuclei in the embryonic region. One of the two paranuclear masses is 
shown lying in the trophamnion beneath the embryonic region. The parasite body 
is entirely surrounded by a cyst of host tissue. 
G. —Section through the twinning stage of the parasite body, which takes place 
about six days after oviposition. The embryonic region has divided, two of the four 
nuclei passing to each half of the twin embryonic regions. The division of the two 
paranuclear masses forms four similar masses. Two paranuclear masses and one of 
the embryonic regions with its two nuclei thus form a germ, and the twin germs 
become separated structurally after the trophamnion infiltrates between the two 
embryonic regions. X2,200. 
H. —A twin germ surrounded by host tissue with the two embryonic regions still 
encased in a common trophamnion. X 1,100 (half the magnification of the preceding 
figures). 
I. —Parasite body which is developing monembryonically while encased in a part 
of the host salivary gland. Four of its eight embryonic nuclei are shown in this 
section. Xi.ioo. 
