592 
MR. B. T. LOWNE ON THE MODIFICATIONS OF 
development of the compound eye : a task which I shall hope to commence at least 
next summer. 
Claparede’s paper, which is most accurate, gives very valuable details on the 
development of the true compound eyed' He has also described and figured the 
various stages of the development of the eye of Formica, but he has neither detected 
the rod-cells of the chamber nor the facellus : I cannot help thinking that this has 
been from the manner in which the stemon separates from the facullus. I strongly 
suspect that Claparede’s preparations represent only a part of the eye, and that in 
the more advanced stage the chamber is only partially represented. Unless this is 
the case, the remarkable deviation in the Hymenoptera from the more usual form of 
the eye in insects is developed from an eye which differs in no important particular 
from the compound eye in its simplest condition. 
The true compound eye of insects is seen in three very different forms in the fully 
developed insect ; but the observations of Claparede show that in the undeveloped 
condition of the eye these are all most probably identical, or nearly so. In this 
condition each segment of the eye consists of thirteen principal cells : eight form the 
cone (Krystalkegel) and five represent the rhabdion. Beside these there is a variable 
number of pigment cells. 
The highly refractive structures of the axis of these parts are probably formed by 
the deposit of chitin in the substance of the primitive cells ; but I think that further 
investigation of the whole subject is needed. Although my observations on the 
development of the compound eye agree in the main with those of Claparede, I have 
yet to work out the subject with the increased knowledge which I now possess. 
The view that the hard and highly refractive parts of the cone or chamber are 
formed in the interior of the primitive cells is borne out, however, by the condition 
of the cone in the Nocturnal and Crepuscuiarian Lepidoptera, and according to 
LeydigI in the eye of Cantharis melanura , Elater noctiluca, and Hypcria, where 
the whole of the large cells of the primitive cone are replaced by the hard scleral 
cone. 
I shall call the form of eye typical of the Nocturnal Lepidoptera the conic eye : and 
shall speak of the conic eye as proto-conic in its embryonic condition, and sclero-conic 
in the form it assumes in the Nocturnal Lepidoptera, and many other insects. 
At present I have not found the proto-conic form of eye in any fully developed 
insect, but I have not yet examined the eyes of the Coleoptera, in which the writings of 
previous observers render it highly probable that such eyes exist, at least amongst the 
Pentamera. The work of Leydig shows that it exists in Melolontha. 
Starting from the conic eye as the nearest approach to the primitive eye, there are 
two very remarkable and opposite deviations. In one, the cone is replaced by fluid, 
and the recipient structures are reduced To their simplest condition, as in the eyes 
* Luc. cit. 
t Luc. cit . 
