238 WM. A. KEPNER AND J. R. CASH 
Fig. 1. An early stage in the formation of the ciliated pit and its ganglion. 
(end.) Endoderm or wall of enteron. (g) General epidermis lowered at (a) 
to form the rudiment of the fundus of pit. Note absence of. cilia in this 
lowered region and migrating mitotic cells (me, m’c’). (mes) Mesodermal 
cells crowded about the forming ciliated pit-ganglion (g). > 1500. 
This sharp depression is already a rudimentary pit with its 
non-ciliated fundus and its ciliated marginal walls but lacks a 
ciliated pit-ganglion. At this time, about the fundus of the 
rudimentary pit mitoses arise which send into the mesenchymal 
space between the fundus and the anlage of the ‘brain,’ which 
has already been formed, a proliferation of cells which radiate 
from beneath the developing fundus of the pit. This mass of 
cells is the beginning of the ciliated pit-ganglion. 
Thus there are established at the outset two parts of the ciliated 
pit. a) The epithelium of the pit; b) The rudiments of a ciliated 
pit-ganglion. 
