THE SIMPLE AND COMPOUND EYES OF INSECTS. 
589 
these cavities are deeply pigmented. Between these cylindrical cavities are others of 
smaller diameter. Each of the larger cylinders contains seven rod-like cells ; the 
smaller ones transmit tracheal tubes. I suspect the rod-like cells represent the facelli 
in the eye of Vespa and Tipula — a view strengthened by, and indeed entirely resting 
upon, the condition of the eye in the Crepuscularia. (See fig. 36.) 
T in m od iately beneath the basal membrane there is a grouping together of the nerve- 
fibres into bundles, which are deeply pigmented with dark brown pigment. Amongst 
these bundles are a number of large stellate cells (p)f all more or less strongly 
pigmented, but bearing a very close resemblance to the stellate nerve-cells of the 
outer ganglion or nervous retina ; together with small round and stellate nerve 
cells (g). Beneath these are numerous elongated fusiform cells (c), arranged in 
bundles like those of the facelloid layer in the retina of the Diptera, but more nearly 
resembling the fusiform cells of the deep ganglion of those insects. The fibres of the 
decussation of the optic nerve, which unite the outer and inner ganglia, are arranged 
in bundles which have the appearance of large nerve-fibres. 
VIII. On a Modification of the Eye in the Diurnal Lepidoptera. (Fig. 35.) 
The only modification I have observed in the Diurnal Lepidoptera is one in which 
the tetraphore is placed near the bottom of an elongated chamber ; this appears to 
occur in Pieris, Colias, and Gonep)teryx : the only three genera in which I have examined 
the .eye, except Vanessa. Eight very delicate transparent cells (c and c") appear to 
fill this chamber (fig. 35). The lens of the corneal facet has a much less curve on its 
outer surface in this form of eye. Owing to an accident in the process of preparation, 
I regret that I am unable to determine from which of these three genera the figure is 
taken, but they are all very much alike in structure. I believe, however, that it is a 
drawing from the eye of Colias. 
Claparede represents a semi- diagrammatic section of the partially developed eye of 
the pupa of Vanessa ; it shows the original condition of the chamber of the eye filled 
with eight cells, in the interior of which the hard structures of the tetrasome are 
developed. The researches of Claparede on the development of the eye in this genus 
are very complete, and throw great light on the morphology of the compound eye.t 
IX. On the Structure of the Eye in the Sphingidce. (Fig. 36.) 
I have not been able to examine the eye in the recent insect, but Prof. Flower 
placed at my disposal a very fine pupa of a Sphinx which had been many years pre- 
served in spirit, from which I obtained some very excellent preparations. 
* These cells are figured by Claparede (loc. cit.) in a drawing of the parts in the mature pupa. 
Judging from his figure, they are probably nervous elements. 
t Loc. cit. 
