OOGENESIS IN PHILOSAMIA 2 
sented by the double chromatin nucleolus, which is interpreted 
as an equally paired heterochromosome. When the threads 
shorten to chromosomes, this is indistinguishable from the others. 
In Abraxas these stages are similar. <A distinction is noted here 
between eggs and nurse cells. In the former ‘‘the bivalent 
threads persist to the latest stage observed—possibly till the 
prophase of the polar divisions;” in the latter, the bivalent threads 
shorten into loops to form chromosomes. [In Bombyx and 
Pieris, as described by Grinberg (03), the germ cells are at 
first all alike, with nucleolus and granules in the nucleus. The 
next zone in the ovary shows spiremes, in which stage synapsis 
occurs. Cell boundaries are not figured here. This is fol- 
lowed by a differentiation zone, in which the egg nucleus is 
distinguished by a nucleolus and threads, the nurse cells by 
tetrads. Details of their origin are not given. Fragmentation 
of the tetrads is described, and the arrangement of nurse cells 
near the egg, followed by a transfer of granular material to the 
egg cell. 
Neuroptera. The observations of Marshall (07) on the ovary 
of Platyphylax are meagre as regards chromatin changes. From 
synapsis, beaded threads appear, showing a lengthwise split. 
These threads give rise to tetrads, which fragment. In cells 
destined to form eggs, the tetrads disappear later and the nuclei 
are slightly larger. The further history of the eggs and nurse 
cells is not given. 
Hymenoptera. In the early ovary of the bee, Paulcke (’00) 
observed that the eggs and nurse cells are at first similar. Beyond 
the synapsis stage, the nurse cells differentiate, the chromatin 
fragmenting and the nucleus increasing in size. Later the 
cytoplasm of the egg may be seen projecting into the region of 
the nurse cells, which are very numerous. He believed that 
nurse cells entire might be taken into the egg, and that amitosis 
occurred. 
Hemiptera. In a study of the early ovary of Protenor, Foot 
and Strobell (11) distinguish three zones in the ovary: Zone 
A consists of nuclei with numerous granules; zone B of larger 
nuclei with granules and a nucleolus, arising by growth from A; 
