430 THOS. H. MONTGOMERY jr., 
13), with a small deep-staining nucleus (N Fig. 8); the cytoplasm 
usually nearly homogeneous, sometimes alveolar, non-refractive. The 
two ends of the cell are attenuated and drawn out into long fibres. 
Those nearest the capsule wall (Z.Cap) are generally found attached 
to it in pyriform clusters; the cells lying deeper in the eye cavity may 
in some cases be seen to be attached to the others. There is not a 
single epithelial layer of these cells, nor do any of them appear to 
be entirely disconnected from the others, but they seem to form a 
connected whole. By iron-haematoxylin staining (Ret. C Fig. 5, Pl. 37) 
deep-staining fibres are to be found within these cells, staining in the 
same way as the chromophilic nerve fibres of the central nervous 
system. In each cell is at least one such fibre, which generally forms 
a loop around the nucleus, the loop often appearing ring-shaped. 
Sometimes a fibre is seen to end against the nucleus (N), but it is 
probable that in such a case the loop encircles the nucleus in such a 
position that it cannot be seen. These intra-cellular fibres may be 
traced to the capsule (Fig. 5 E.Cap), and there seem to enter the 
nerve bundles (Dors. N. B) of the latter; the terminal ends of these 
fibres become much attenuated, which would speak for their being 
outgrowths from the retinal cells into the nerves rather than chromo- 
philic nerve fibres which have grown into these cells from the nerve 
bundles. These cells have a considerable resemblance to the small 
sensory cells found within the thickened hypodermis of the tail lobes 
of the male. 
There can be doubt as to the correctness of interpreting this 
structure as a sense organ, its rich nervous supply alone justifies this 
view. It might be an organ of touch, but more probably it is an 
organ for the perception of light, when one considers the transparent, 
thin cuticula on its anterior surface, the arrangement and more or 
less isolation of the long hypodermal elements below this (which do 
not appear to be sensory but simply conductive), the space with a 
clear fluid, and the nervous elements behind this. In an immature 
female from an Acheta in which the cuticula was still thin and white, 
this organ appeared much as in the adult and its cavity nearly filled 
with small cells; and since in this individual the organ was smaller 
than in the adult stage it probably reaches its maximum development 
and specialisation in the adult. The retinal cells are perhaps de- 
rivatives of the hypodermis, sensory elements which have separated 
from it. It is an eye of a unique character, and lacks pigment. 
However, around the posterior region of the head is found the black 
