MAUTHNER’S CELL 103 
laterals of VIIIth fibers. The club-endings are the important 
. part of the synapse and they constitute an unique feature of the 
siluroid brain.- As the root fibers retain their thick myelin 
sheaths almost to the very end, the whole apparatus appears 
striking in transverse and horizontal series of hematoxylin, Weig- 
ert and Cajal preparations. | 
Since the elements of the synapse are very large, it is an ex- 
ceptionally favorable material for the study of the nature of the 
synapse. The results of my study are.embodied in figure 13, 
which was drawn from an adult brain fixed in formol-osmic- 
Zenker. In this and in all of the other brains fixed in strong os- 
mic acid mixtures the plasma membranes around the club-end- 
ings of the VIIIth root fibers stand out very clearly. The same 
may be said of the limiting membrane of the lateral dendrite 
where it is cut squarely. In other words, there is no evidence 
of fusions between root fibers and dendrite; the two are merely 
in contact. The few insignificant branches of the lateral den- 
drite which might be interpreted as root fibers fused to the den- 
drite are readily distinguished from them by the facts that they 
taper down rapidly peripherally and have no myelin sheaths. 
The ventral dendrites. In most teleosts there is but a single 
large ventral dendrite, as is shown in figure 6 for the trout larva 
(S.Veni.Dend.). Here it is as mighty as the lateral dendrite, it 
extends rostrally as well as ventrally and is profusely branched 
in the neuropil at the periphery of the oblongata. In Ameiurus 
the largest and most medial of the ventral dendrites (the superior 
ventral dendrite) has the same direction and position, as appears 
in figure 3. In this fish, however, there is always another ven- 
tral dendrite (inferior ventral dendrite) which reaches the ven- 
tral-lateral periphery. It is never so large or so profusely 
branched as the superior dendrite (fig. 11, Inf.Vent.Dend.); it 
arises laterally from the cell body and is directed caudally as 
well as ventrally (see fig. 3, left Mauthner’s cell). In the cell 
reconstructed in figure 11 there were two such dendrites which 
is not a rare condition. 
The two great ventral dendrites have certain distinct connec- 
tions as well as different relations to the cell body. It has been 
