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 talfen 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 JOTJRNAIi OF COMPAHATIVE NBtTSOLOaY, VOL. 27, NO. 1 



