A6 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
gewinnen.” Through this turning the ‘‘urspriinglich abwirts ge- 
richteten Kintrittsstellen der Nerven in die Retina”’ came to assume 
a more lateral and superficial position, and so the more or less dis- 
tinctly inverse form of the eyes has arisen. We must admit that 
the parts of the eye do not begin their dey elopment in the positions 
which they come to occupy in the adult; but in Eucalanus the change 
has not brought about inversion of the retinal cells. Hesse (:01, 
p. 353) takes a view similar to that of Claus. He is of opinion that 
the inversion of the median eye of Crustacea occurs because visual 
cells, which have migrated out of the epidermis, have become oriented, 
for physiological reasons, with the sensitive portions directed toward 
the pigment; later the cup about the cells is formed by the incurving 
of the pigmented shell. It is probable that the relative positions of 
the ventral and lateral ocelli are to be interpreted as indicating that 
the lateral eyes in such forms as the Pontellidae are originally portions 
of the median eye. Leuckart (’59, p. 260) seems to be of the opinion 
‘that the eyes of Anomalocera, which are provided with lenses, are 
independent of the median eye, in the sense that the latter is the equiva- 
lent of the eye of Cyclops. Claus (59) at first accepted this view, 
but later (63, p. 46) was led to believe that the lateral eyes of Pon- 
tellidae might be considered as originally belonging to the median eye 
Ina siibsequctt paper (Claus, 91, p. 247), however, he again sdbpied 
the interpretation of Leuckart and states (p. 250) that the dorsal eyes 
of the Pontellidae must be very different from the median eyes, and 
are to be homologized with the compound, facetted, eyes of Arthropoda. 
Parker (91) nas shown that the lens eyes of Pontella are entirely 
separated from the body ectoderm, while the compound eyes of the 
Decapoda are continuous with the hypodermis. Those of the Clado- 
cera and Branchiopodidae are of an intermediate type. Hesse (02, 
has adopted a similar classification as regards the higher Crustacea 
and Arthropoda in general. With this I agree, and consequently, I 
think we cannot adopt the view of Claus (91, p. 250), that “Wir 
haben also die interessante Thatsache zu constatiren, dass auch unter 
den Copepoden [Pontelliden] das bei den Phyllopoden und auch Cirri- 
pedien schon so hoch entwickelte zusammengestzte Augenpaar vertoe- 
ten ist.” Whether the lens eyes of Pontella are compound or not, 
they must be looked upon as of an entirely different type from those 
of the Decopoda or Phyllopoda and Cladocera. 
But as regards Eucalanus, the conclusion seems to me to be warranted 
that the lateral ocelli are subepidermal and, in that particular, of the 
same type as the lateral eyes of Pontella. The axes of the cups are 
