80 BULLETIN OF THE 
Lenses similar in position to those in Pontella have been identified 
in the lateral eyes of several other genera of Copepods. Gegenbaur 
(758, p. 71) described such lenses in Sapphirina, and Leuckart (°59, 
p- 250) observed similar ones in the lateral eyes of Coryczus and 
Copilia. In all these genera the lenses, although biconvex, are not 
spherical, as in Pontella, Gegenbaur (’58, p. 71), following Leydig’s 
generalization, believed that in Sapphirina the lenses were thickenings 
in the cuticular covering of the body, and Claus (’59, p. 271) considered 
them morphologically equivalent to a single corneal facet. Leuckart 
(759, p. 250), without definitely committing himself as to the nature 
of the lens, states that in Copilia and Coryceus the lens is implanted 
in the superficial cuticula, and further describes it in Coryceus as com- 
posed of two parts, an outer and an inner. According to Grenacher 
(79, p. 67), both parts can be identified in the lens of Copilia; the 
outer part is a portion of the superficial cuticula; the inner part, both 
in its optical properties and its behavior toward reagents, is unlike the 
cuticula. The inner part, however, contains no traces of cells, but is 
composed of a homogeneous substance, probably secreted. This view of 
the duplicity of the lens contrasts with the older idea of its origin as a 
thickening in the superficial cuticula. 
It is possible that the lenses in the Pontellide and Coryceide are not 
homologous structures, but on account of their similarity I am inclined 
to consider them as such. Since in Pontella both parts are derived 
from the cuticula, I believe that a similar origin will be demonstrated 
for these parts in the Coryceide. The differences which Grenacher 
has pointed out between the two parts of the lens in Copilia do not 
necessarily oppose this view. It is possible that the cuticular secretion 
which forms the proximal part of the lens may originate separately 
from the other cuticula, as in fact it does in Pontella; and it may also 
be true, although this is not supported by the condition in Pontella, 
that the two parts, although both secretions of the hypodermis, may 
differ enough in their substance to account for all the peculiarities ob- 
served by Grenacher. 
The retina and lens in Pontella are not separated by an intervening 
space as in the Coryceide, but are in immediate contact. The retina 
is composed of a mass of cells, the number and arrangement of which 
can be seen in the figures on Plate III. These figures represent a 
series of consecutive sections cut in planes transverse to the axis of 
the eye, i. e. parallel to the horizontal plane of the animal (compare 
Fig. 18, Plate II.). The series is complete in that it represents all 
