No. 1.—CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 
OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD 
COLLEGE, UNDER THE DIRECTION OF E. L. MARK, No. 196. 
The Light Recipient Organs of the Copepod, Eucalanus elongatus. 
By CALVIN OLIN ESTERLY. 
I. Introduction and Methods . 
II. The optic apparatus . 
1. The median, uninverted, 
eye 
a. Location 
features 
b. Pigment mass. 
ce. Basal plates ; 
d. Number and _arrange- 
ment of the retinal cells 
e. Interior bodies (phao- 
somes); their arrange- 
ment in the cells . 
f. Relation of axis cylin- 
ders to retinal cells 
g. Numerical relation of 
nerve fibres and visual 
cells Br hoy 
h. The neurofibrillae 
and general 
CONTENTS. 
PAGE 
3. | i. Relation between neuro- 
land 
( 
7 
9 
-, 
11 
13 
45) | 
fibrils and ‘ interior bod- 
ies ”’ ee 
j. Parts of the eye in their 
relation to the hypo- 
dermis PMS 
2. The ‘‘inverted”’ eyes or 
“organs of Claus” 
a. Location 
b. Composition , 
ce. Similarity in structure 
to the cells of the median 
eye ababiegihs enter j 
d. Relation of nerves to 
organs of Claus 
III. Discussion . 
IV. Summary . 
_ Bibliography . 
Explanation of plates . 
I. Introduction and Methods. 
PAGE 
30 
ol 
35 
30 
36 
36 
38 
39 
50 
52 
55 
ALTHOUGH the decapod Crustacea have been the objects of much 
careful morphological 
investigation and experimentation, in_ the 
fields of comparative. neurology and psychology, the organization of 
the nervous system of the lower Crustacea has been almost entirely 
neglected in the neurological studies which have been made in the 
last fifteen years. 
Since the appearance of the papers by Richard (91) and Claus 
(91), practically no study has been made of either the central or 
3 
