286 Annals Entomological Society of America [Vol. VIII, 
body cavity of allimmature insects. The arrangement of these 
glands is in metamerical groups on both sides of the abdomen in 
conjunction with the spiracles. The cells are usually separate 
spherical individuals which lie enmeshed or suspended in a 
tangle of fine trachea with which, however, there is no closer 
connection than that of contact. 
The origin of these cells is ectodermal. They arise in the 
form of a chain by amitotic division from one cell ventro-caudad 
of each spiracle. From this chain they migrate to their final 
positions. Before the egg hatches the ultimate number of cells 
in each group is reached and no further division takes place. 
These glands persist often into the imaginal stage. The secret- 
ing of the cell is a periodic function that takes place even in the » 
embryo. While in the process of secreting the nucleus forms a 
honeycombed structure and from this long mitochondrial fil- 
aments extend to the periphery of the cell. The papers of 
Holland and Stendell contain good cenocyte reviews and nearly 
complete bibliographies. 
The study of the mitochondria from an architectural point 
of view has largely been confined to the investigation of the 
origin of the highly specialized nerve and muscle fibrils. The 
cenocytes afford an opportunity of studying these structures 
comparatively free from the specializing influences of mechan- 
ical stresses or pressures. The cells originate while the egg is 
still in a semiplastic state. Immediately on being formed they 
float away in the body fluid till they come to rest 1n the delicate 
meshes of the trachea. For this reason any elemental structure 
in the cells of the primitive ectoderm might persist through the 
intervening generations into the make-up of the cenocytes. 
With the exception of the eggs the cenocytes are the largest 
cells to be found in the insect body. This of course has the 
obvious advantage of making them easy to study. On the 
other hand when one considers that they are many times the 
size of the parent ectodermal cells, the question naturally arises 
as to whether a primitive intracellular network would meet this 
demand for expansion by the addition of more network or by 
the stretching of the original. From the observations of the 
cenocytes it would appear that the latter process is the one that 
occurs. The network is very open and it is this feature of size 
that makes it so very distinct. 
