100 GEORGE W. BARTELMEZ 
off collaterals to the motor nuclei. I have little to add to the 
excellent descriptions of Tagliani (’05) and Beccari (’07); I would 
say, however, that there is no evidence in my material of fusions 
such as Beccari describes between the collaterals of Mauthner’s 
fiber and the dendrites of ventral horn cells. ‘These collaterals 
are more obvious, and I am inclined to believe more abundant, 
in the young larvae than in older larvae and adults, as Tagliani 
says. 
The great size of Mauthner’s cell becomes apparent when in 
the reconstructions it is compared with the Miiller’s cells and the 
cells of the nucleus motorius tegmenti (figs. 3-5, and 7-9) or 
with the outlines of the large cells of Deiters’ nucleus (fig. 6). 
It is always difficult to calculate the size of a multipolar cell, but 
an estimate will give a fairly concrete idea of the differences be- 
tween Mauthner’s cell and the other cells of the nucleus motorius 
tegmenti. Measuring from the sections of a young adult (fig. 
7) the cell body (perikaryon) measured 66 x 63 X 604. If the 
dendrites be taken into account, the volume would be tripled. 
’ The dimensions of the Miiller’s cell shown in figure 8 are 63 x 30 
< 26 wu. The total volumes would be related as about seven to 
one, yet in this case the Mauthner’s cell nucleus is but very little 
larger in actual size than that of the Miiller’s cell; the usual rela- 
tion of the diameters is as one to one and a half. It is clear, then, 
that the nucleus of Mauthner’s cell is small in comparison with 
the cytoplasm (see especially figs. 6, 10 and 11). The same 
holds true for the Miiller’s cells as may be seen at a glance in 
figures 8 and 9. 
Dendrites. Certain dendrites of Mauthner’s cell are constant 
in their position and connections. In the typical and simplest 
forms there are two gigantic dendrites and numerous small ones. 
This is the condition described by Mayser (’82) in Cyprinoids, 
Beceari (’07) in Salmo and Salamandrina, Tello (’09) in Salmo, 
Leuciscus and Cyprinus, C. J. Herrick (14) in Amblystoma, and 
I have found it to be the case in all of the teleosts studied except 
Ameiurus. Figure 6, reconstructed from the brain of a 32 mm. 
trout larva, shows the lateral dendrite (Lat.Dend.) of authors 
and the ventral one, which will be called the superior ventral 
