242 WM. A. KEPNER AND J. R. CASH 
Fig. 3. Later stage in formation of ciliated pit and ganglion. Note appear- 
ance of ‘homogeneous mass’ (hm), with rhabdites (rh) yet present in the fun- 
dus epithelium. Ciliated pit-ganglion (g) has now fused with the fibrous part 
of the ‘brain’ (br); (end) Constricted enteron. (c) Commissure of ‘brain’ 
forming. > 1500. 
The interesting outcome of this development is a sensory 
epithelium from which many cells have retreated, leaving be- 
hind a low, secreting epithelium through which they leave elon- 
gated processes of themselves. Figure 2. These processes are 
the sensory ends of the ganglionic cells which have been de- 
scribed. Thus we have the development of a ciliated pit whose 
marginal cells are covered with extremely long cilia which may 
protect the delicate fundus against impacts of external objects 
by practically closing the mouth of the pit to any particles of 
matter which might enter and in any way injure the sensitive 
’ Tt cannot be definitely stated that all ot these ganglionic cells have such 
processes, since on account of the nature of the case, only a few such processes 
in each animal can be sectioned parallel to their axes. 
