256 
F. G. HEATHCOTE. 
folds and irregularities into which it is thrown (fig. 3, hy.). 
Their nucleus is larger and stains more deeply. At the lateral 
ventral lip (fig. 2, Ivl .) the cells are more elongated and more 
closely packed together, and gradually take the character of 
the sensory epithelium which forms the greater part of the 
lining of the pouches. These sensory cells are long and 
columnar and at their outer ends are prolonged into a blunt 
projection of less diameter than the rest of the cell (fig. 7 , oe .) 
and about one third the length of the whole. At the folds 
which bound the median recess the cells lose their sensory 
character and take the form of the ordinary hypodermic cells. 
The mass of sensory cells at the top of the median recess which 
are continuous with the hypodermic cells are of a character 
distinct from those described as lining the pouches. They are 
of irregular elongated shape and resemble ganglion-cells, the 
inner end' being sometimes bifurcated (fig. 6, Bi..). The sensory 
epithelial layer is of considerable thickness (fig. 2). 
I have hitherto spoken of the epithelial layers simply as in- 
vesting the chitinous pouches with their hairs, but I will now 
consider the means by which the hairs and cells come into 
relation. There is no doubt that the terminal parts of the 
sense cells project into the depressions (fig. 3) in the chitin, 
caused by the folds spoken of above, and that each chitinous 
hair is inserted into the chitin immediately outside this pro- 
jecting part of a sense cell. I am also inclined to believe, 
though, owing to the small amount of material at my command 
my evidence on this point is not conclusive, that the bases of 
the chitinous hairs, i. e. the part which projects on the inner 
side of the chitinous lining, have a small cavity in their basal 
parts, into which a threadlike prolongation of the sense cell 
projects. 
I have invariably found foreign bodies in the median and 
lateral recesses, and as the latter are in communication with 
the exterior they may possibly be grains of dirt or sand, but 
I think that they may be concretions. 
