NUCLEAR SIZE OF NERVE CELLS 71 
the deuto-cerebron or antennal lobes. These latter arise from 
the ventro-anterior side of the dorso-cerebron by two stalks of 
fibrillar substance. Each stalk expands into a convoluted spheri- 
cal mass of fibers from which the nerves of the antennae arise. 
This fibrillar core is surrounded by nerve cells. In the adult 
these cells are of three types as far as nuclear size is concerned, 
which conform to the types described by Kenyon. These are, 
multipolar giant cells, large and small ganglion cells. In the 
larva and pupa we find large neuroblasts which give rise to the 
cells of the last two types by mitosis and finally themselves 
transform into the giant cells of the adult. 
It is manifestly impossible to measure all the nuclei in any . 
ganglion in such a study as this. We must be content to choose 
and select with as much care as possible, such cells as appear to 
belong in the same general group and from a study of their 
measurements attempt to gain some insight into the problems 
which concern the whole mass of cells. Such cells in each class 
were chosen as appeared to be fair representatives of the respec- 
tive groups. It is probable that others in going over the same 
material would select and measure other cells and so arrive at 
average measurements somewhat different from those given in 
our tables. Our experience leads us to believe, however, that 
the general form of the curves derived from a study of the data 
would not be materially altered. 
Usually we have found no difficulty in making a decision as to 
the group in which any particular cell belongs. There have been 
a few instances, however, where the mere matter of size seemed 
to be insufficient to control the matter of classification. In such 
cases we have taken into consideration the general appearance 
of the cells, both as to nucleus and cytoplasm, before placing the 
cell in one or another group. In the case of the giant cells care 
was taken to choose those in which the plane of section passed 
approximately through the center of the nucleus. 
Each nucleus was measured in its longest and shortest. diame- 
ter and the average of these taken as the mean diameter. The 
results of these measurements are summed up in the following 
table which gives the average nuclear diameter for the three 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 27, No. 1 
