No. 2.] THE MORPHOLOGY OF DERO VAGA. 159 
There are twelve well-defined organs in the greater band, six 
large and six small (Pl. XIII, Fig. 9; Pl. XIV, Figs. 11-13). 
In the lesser band there are eight organs, two large and six 
small. These organs have a very constant, regular arrangement 
in each band so that the organs in corresponding bands form 
longitudinal rows which extend the whole length of the body, — 
in all twenty rows. 
The rows containing the larger organs are the two median- 
dorsal rows (m.s.0.), the two dorso-lateral (d-/.s.0.) occurring just 
below the dorsal setae, the two lateral rows (/.s.0.) occupying a 
position just below the so-called “lateral line,” and the two 
ventro-lateral rows (v-/.s.0.) which are found immediately above 
the ventral setae. The lateral rows only are made up of organs 
occurring in the lesser bands. 
The sense organs in the living worm appear as hemispherical 
elevations of the epidermis and are set with hairs. The diam- 
eter of these elevations varies from .o175 to .025 mm., and the 
elevation above the surface is about .0125 mm. The hairs have 
a length of .o175 mm. After the animals have been subjected 
to the killing reagents, the organs are found to be, in most 
cases, level with the surface of the epidermis. 
The organs are very simple in their structure, consisting of 
sensory cells alone. Covering cells have not been observed. 
The sense cells (s.c.) are elongate with enlarged middle portion 
and have large nuclei which stain deeply with the ordinary 
reagents, but remain clear when treated with gold and silver. 
Each cell bears a long stiff hair. The inner end of the cell in 
many cases rests directly on the lateral nerve from the ventral 
cord (Pl. XIV, Fig. 16, /..); otherwise no direct connection has 
been observed between cells and nerves. 
The sense organs in the greater band occur on the second 
lateral nerve (/.7.2), while those in the lesser band are found in 
connection with the fourth lateral nerve (/.z.4). The first well- 
defined band of organs on the body is innervated by the fourth 
nerve from the dorsal ganglion. 
