104 BULLETIN OF THE 
to me to involve that of the origin of the similar cells beneath the 
retina. If I am right in this conclusion, all these,cells must either have 
arisen in the retina, many of them migrating in a proximal direction 
out of it, or they must have had some extra-retinal origin, some of them 
migrating into it. On account of the considerable numbers in which they 
exist in the spaces below the retina, it seems to me much more probable 
that they have had an extra-retinal origin than that they have come 
from the retina itself. If this is their source, it is evident that those 
which are in the retina are intrusive. The nucleus which has already 
been mentioned as caught in an opening of the basement membrane 
(Fig. 91) has more the appearance of a body which is making its way 
into the retina than of one which is moving in the reverse direction, 
and may therefore be regarded as confirming to some extent the view 
of the extra-retinal origin of these cells. Their source, however, cannot 
be stated with certainty. Their power of migration implies amceboid 
activity, and this might be taken as an indication of their mesodermic 
origin. 
The following cells characterize the ommatidium of Mysis: cells of 
the corneal hypodermis, two: cone cells, two ; proximal. retinular cells, 
eight, one of which is rudimentary ; distal retinular cells, two; accessory 
pigment cells (mesodermic ?) present. 
Stomatopoda. 
The material which I have had for the study of the eyes in the Stoma- 
topods consisted of two specimens of Gonodactylus chirarga, Latr. These 
were kindly given me by Mr. W. S. Wadsworth, who had collected them 
in the Bermudas. One of them had been killed in hot water and pre- 
served in alcohol; the other was both killed and preserved in strong 
alcohol ; both were in excellent histological condition. 
In Gonodactylus, as I have previously mentioned, there are two kinds 
of ommatidia ; these differ in no important respect except size. 
Longitudinal sections of both kinds are represented on Plate VIII. ; 
the figure of the larger kind (Fig. 94) is taken from a depigmented sec- 
tion, that of the smaller one (Fig. 95) from a section containing the 
pigment in its natural condition. In the following description I shall 
give an account of the structure of the larger ommatidia, alluding to 
the condition of the smaller ones only when it differs in some important 
respect from that of the others. 
The corneal hypodermis is represented in the ommatidium of Go- 
nodactylus by two cells, the nuclei (Figs. 94-96, nd. ern.) of which can 
