(2 tie) 
the basilar membrane being a retina or commencement of the 
percipient portions of the eye, and called the parts in 
question the terminal anastomoses and the periopticon; he 
also re-affirmed very strongly as correct the views of Grenacher 
and the numerous authors who had agreed with him, that the 
retinule are the percipient parts. Patten has more recently 
made an investigation of the structure of the ommatidium, 
and states a totally different view; he locates, in a most 
positive manner, the seat of perception in the crystalline 
cones, a view which had been asserted by one or two earlier 
authorities, but had been almost abandoned. Thus, then, 
we have the latest three authorities locating the seat of vision 
in three totally different parts of the eye. 
It is not my province, even if I were capable of doing so, 
to attempt to determine how much value there is to be 
attached to all or either of these views; but I will just 
recall the fact that the compound-eye, speaking roughly, may 
be divided into three parts: 1, the outer part consisting of 
the structures from the outer facets to the apices of the 
crystalline cones; 2, the intermediate structures between the 
cones and the basilar membrane: and 3, the structures 
within the basilar membrane. Now, the authorities I have 
mentioned are confident that a percipient layer exists in each 
of these different zones. It is clear, then, that the function 
of the compound-eye cannot at present be determined by 
anatomical knowledge, but that it is probable that the func- 
tions of the eye may be complex,—indeed, that there may 
actually be two or three different sets of perceptive structures. 
It is true that each of the anatomists I have named is pretty 
confident as to the correctness of his own view, but I am 
inclined to think that it is possible that neither of them has 
given sufficient attention to the idea that the existence of one 
percipient layer does not necessarily prove the non-existence 
of another. Whether this prove to be the case or not, it is 
quite certain that the nervous structures in connection with 
the compound-eye are most remarkably perfect and complex. 
Hickson does not hesitate to express his admiration of their 
extent, and it is evident that the number and variety of the 
nervous structures of the insect’s eye are not the least amongst 
