244 WM. A. KEPNER AND J. R. CASH 
epithelial cells could be seen passing through the homogeneous 
mass,” and that—‘“‘the cilia on the small cells at the base of the 
pit are like those of the epithelial cells of the integument except 
that they are much longer. They range from 8 micra to 15 
micra in length.’ We have found that the cilia on the marginal 
walls of the pit are longer than those on the general surface of 
the body but have found in no case any suggestion of cilia re- 
lated to the fundus of the pit or its ‘homogeneous mass.’ Accord- 
ing to Ott,® Landsberg says “‘that the bottom of each pit is covered 
with a thick layer of homogeneous substance which may be re- 
garded as mucus. Below this is a thin layer of ciliated epithelial 
cells whose cilia project through the homogeneous layer. Next 
to this is a much thicker layer which is made up of mostly pyri- 
form cells, although there are other histological elements scat- 
tered through it. Next to this layer is the ganglion which is 
connected with the nerve.’ This description is very much in 
accordance with our results with the exception of the statement 
that there are cilia on the low cells at the fundus of the pit. 
Ott says “There are three possible methods by which the three 
layers described by Landsberg might be produced: 1) By a 
division of the epithelial cells, 2) by a migration of cells from the 
brain ganglia to the walls of the pits, 3) by a migration outward 
of some of the epithelial cells to form a second outer layer. If 
a new layer of cells was formed by the first method we ought cer- 
tainly tofindnumerous spindles vertice to the surface in every de- 
veloping pit.’”® Now we have assumed the first mentioned 
method of formation of the ciliated pit ganglion mainly on 
account of the fact that we have seen these numerous spindles as — 
described by Ott (fig. 2). We find them in nearly every section 
that passes through the fundus and ganglion. 
In one other respect our conclusions differ from a previous 
description of the general structure of the pits by von Graff 
(13). He says “Das Nervensvstem besteht aus zwei lang- 
gestreckten Halften, deren jede durch eine swache EKinschniirung 
4 Jour. Morph., vol. 7, p. 291, 1892. 
5Same reference, p. 291. 
6 Same reference, pp. 292-8. 
