1917-18.] Germ-Band in the Egg of the Holly Tortrix Moth. 159 
material becomes more evenly distributed throughout the cells. The 
completion of the blastoderm is achieved when the cells become sufficiently 
numerous to form a continuous epithelium. 
The Polar Bodies. 
Henking, in his investigations on the polar bodies of insects, established 
the fact that, synchronising with the second maturation division of the 
ovum, the first polar body undergoes a division the result of which is a 
pair of daughter nuclei, or simply a pair of twin chromatin masses with 
no nuclear boundary. He further found that, in the majority of cases, a 
fusion — more or less complete — took place between the chromatin of the 
second polar body and that of one of the daughter nuclei of the first polar 
body. According to this author, the body thus formed — the “ Richtungs- 
kopulationskern ” — becomes ultimately absorbed without undergoing any 
further change. The other daughter nucleus of the first polar body also 
disappears. In the case of Pieris brassicce, however, he states that all 
three polar bodies ( i.e . the two daughter nuclei of the first polar body and 
the second polar body) are true nuclei, and that they all fuse together ; but 
he did not follow the fate of the nucleus resulting from this fusion. 
Nachtsheim, in his study of the bee’s egg, observed that at the time 
of the first division of the zygote nucleus a spindle of “ astonishing ” size 
simultaneously forms in the “ Richtungsjdasma,” owing to the division of 
the “ Richtungskopulationskern,” which arose as the result of a union 
between the second polar body and the inner daughter nucleus of the first 
polar body. In the metaphase of this spindle he counted 32 chromosomes, 
though 16 was the number to be expected from the fusion of 8 + 8. I 
quote his explanation : — “ Has plotzliche Auftreten von 32 Chromosomen 
ist so zu erklaren, dass die Chromosomen der Richtungsspindel 
‘ Sammelchromosomen ’ darstellen, die nach den Reifungsteilungen wieder 
in Chromosomen von niedriger Wertigkeit zerfallen.” This large spindle 
does not go on to form daughter nuclei, but fragments into daughter 
spindles and thereafter gradually disappears. 
Owing to my initial lack of experience in cutting the eggs, in many 
of my early sections the delicate “ Richtungsplasma ” was injured, but a 
successful series of sections was made from an egg; which had been fixed 
between two and three hours after oviposition, and in which the zygote 
nucleus had divided into two, these two nuclei being in process of division. 
The “ Richtungsplasma ” of this egg is show T n in figs. 2a and 2b, which 
were drawn from two consecutive sections. Fig. 2a might be interpreted 
as representing a large spindle, such as Nachtsheim describes, fragmenting 
