590 
ME, B. T. LOWNE ON THE MODIFICATIONS OF 
The eye in Sphinx is quite intermediate in structure between that of the Nocturnal 
and of the Diurnal Lepidoptera. 
Immediately beneath the cornea, which was still in an undeveloped state in the 
pupa examined, are four small cells containing nuclei (a) ; these rest upon a hard cone, 
consisting of four segments (a). This structure is characteristic of the eyes of the 
Nocturnal Lepidoptera, and it is perfectly clear in recent specimens. It persists in the 
dried insect, like the other chitinous structures. It had assumed an amber colour in 
the Sphinx pupa from which this description is taken (fig. 36, a). Immediately beneath 
the cone, as I shall call this body, is the rhabdion (a"). This differs in no way from 
that of Vanessa, except in its greater length, and in the fact that its outer end was 
much contorted. Beneath the rhabclia is a layer of undoubted and true facelli (/): 
one to each ocellulus. Each facellus consists of seven cells, the slender prolongations 
of which pass into the corresponding rhabdia. The facelli are surrounded by nucleated 
pigment cells and are continuous with the nerve -fibres. These are gathered together 
into bundles and unite into nerve-trunks (st) ; the fibres from thirty or forty facelli 
being united into a single trunk. They are deeply pigmented with violet-coloured 
pigment. At their inner extremity the bundles of nerve-fibres branch, and are con- 
nected with stellate nerve-cells. The other structures of the retinal ganglion were 
not distinguishable. The nerve-fibre bundles appear to represent the stemon of the 
semi-compound eye of Vespa and Tipula. 
X. On the Structure of the Eye in the Noctuid Moths. (Figs. 37 to 42.) 
At present I have only examined the eye in the true Noctuids. As in the Crepus- 
cularia, there are four cells ( a ) immediately beneath the cornea, but in some species 
these cells each contain one or two bright highly -refractive nuclei, which appear to be 
formed of the same material as the deeper cone (figs. 38 and 42). The nuclei are rod- 
like, and have their long axes at right angles to the corneal facet. These cells rest 
upon a cone (a) formed of four segments, like that in the eye of the Crepuscularia. 
In some Moths this cone is surrounded by pigment cells which form four lines, one 
adjacent to each segment of the cone (fig. 38), and give off numerous moniliform 
fibres, which entirely surround the cone ; in other species the cells are reduced to the 
magnitude of minute granules, from which the pigment fibres of the chamber are given 
off (fig. 37). 
The inner extremity of the cone is continued inwards, in the form of four exceedingly 
fine, highly refractive threads {a”). These are, I believe, always surrounded by a proto- 
plasmic sheath in the recent condition ; but in a great many of my preparations the 
sheath has disappeared, and nothing is left but the highly refractive axial threads. 
They form the rhabdion. It is not uncommon to find these rhabdia united into 
bundles which form a network, and in some species the rhabdia are united into complex 
bundles, which are enclosed in chitinous sheaths surrounded by a large amount of 
pigment (figs. 39 and 40). 
