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 Calvix Olin Esterly. 



CONTENTS. 



general 



I. Introduction and Methods . 



II. The optic apparatus . . . 



1. The median, uninverted, 



eye 



a. Location and 



features . . 



b. Pigment mass . 



c. Basal plates . 



d. Number and 

 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 



h. The neurofibrillae 



PAGE 



3 



9 



9 



11 



13 



15 



21 



23 



28 



PAGE 



i. Relation between neuro- 

 fibrils and " interior bod- 

 ies " 30 



j. Parts of the eye in their 

 relation to the hyjjo- 



dermis 31 



2. The " inverted " eyes or 



" organs of Claus " ... 35 



a. Location 35 



b. Composition .... 36 



c. Similarity in structure 

 to the cells of the median 



eye 36 



d. Relation of nerves to 

 organs of Claus ... 38 



III. Discussion 39 



IV. Summary 50 



Bibliography 52 



Explanation of plates . . .55 



I. Introduction and Methods. 



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 



