CILIATED PITS OF STENOSTOMA 
WM. A. KEPNER AND J. R. CASH 
University of Virginia 
FOUR FIGURES 
The material for this paper was found upon glea and sediment 
deposited upon submerged leaves and twigs taken from both 
near the surface and the bottom of pools in the vicinity of the 
University. 
The animals are about | to 2 mm. long and 200 micra broad at 
the widest region. The body is oblong, spindle shaped, and 
is widest in the region of the mouth; it is grayish white and its 
epidermis, which contains rhabdites, is thickly covered with 
short cilia. The mouth is on the ventral side, about 150-200 
micra posterior to the anteriorend. The urinary system consists 
of a single nephridium. 
The ciliated pits are by far the most striking organs of the 
body which are externally visible. These are small invagina- 
tions in the epidermis which are located lateral-dorsally about 
100 micra from the anterior end of the body. Their shape is, in 
general, similar to small sacs, but their lateral walls are highly 
contractile so that the pit may be made to assume the form of 
a deep cut or that of a shallow, concave disc. The ciliated pits 
have a diameter of about 50 micra and a depth of about 40 micra. 
This paper is concerned with the minute anatomy of the 
ciliated pits and their development. In order to carry out such 
a study the animals were fixed in Flemming’s stronger fluid, which 
consists of 15 parts 1 per cent chromic acid, 4 parts 2 per cent 
osmic acid, 1 part glacial acetic acid; time of fixing 25 minutes. 
Chrome-aceto-formaldehyde, hot and cold solutions of aceto- 
sublimate, and Zenker’s fluid were all tried, but without success, 
235 
