MUSEUM OF COMPARATIVE ZOOLOGY. 99 
had the opportunity of studying the eyes in Nebalia, I can offer it 
merely by way of suggestion. 
Probably two kinds of accessory cells are present in Nebalia ; one of 
these extends from the corneal cuticula to the basement membrane, the 
other, the presence of which is not so fully established, probably occurs 
near the basement membrane. 
Cumacee. 
Excepting what is contained in Burmester’s (’83, pp: 35-37) account 
of the degenerate eyes in Diastylis (Cuma) Rathku, nothing, I believe, 
is known of the finer structure of the eyes in the Cumacee. The speci- 
mens at my disposal for the ‘study of these eyes proved upon examina- 
tion to be blind. At least, the optic plates of all the individuals which 
I examined, both when studied from the exterior and when examined 
in sections, showed no evidence of eyes. My material consisted of 
specimens of Diastylis quadrispinosa, G. O. Sars, and of three other un- 
determined species, two of which belonged to the genus Diastylis and 
one to Eudorella. These were kindly sent me by Prof. S. I. Smith. 
Schizopoda. 
The species of Schizopod the eyes of which I have studied is Mysis 
stenolepis, Smith. Specimens of this Crustacean were kindly collected 
for me at Wood’s Holl, Mass., by Mr. C. B. Davenport. I am also 
under obligations to Dr. H. V. Wilson, of the United States Fish Com- 
mission, who at my request sent me specimens of this species freshly 
preserved in Miiller’s fluid. 
In several of the previous accounts of the eye in Mysis the nuclei 
of the corneal hypodermis, although recognized, have been described as 
Semper’s nuclei, i. e. as nuclei of the cone cells. The differences between 
the hypodermal nuclei and those of the cone cells can be easily seen in 
Mysis stenolepis (Plate VII. Fig. 73). In this species the hypodermal 
nuclei (nJ. crn.) lie in a plane somewhat nearer the external surface of 
the eye than the nuclei of the cone cells (nl. con.). In transverse sec- 
tions at the proper levels, each ommatidium will be seen to contain two 
elongated nuclei (Fig. 75, /. crn.) belonging to the corneal hypodermis, 
and two oval nuclei (Fig. 76, nd. con.) in the cone. The hypodermal 
nuclei occupy such positions that the plane of separation between their 
cells would be at right angles to that between the cone cells (compare 
Figs. 75 and 76). The group of four nuclei, two belonging to the corneal 
