No. 2.— The Compound Eyes in Crustaceans, By G. H. PARKER.) 
TABLE OF CONTENTS. 
Pace PAGE 
T Introduction’. 3s 2." * 40 GP In'Cumaces «3 2152 099 
II. The Retina ema Sean 47 7. In Schizopoda ....-, 99 
Ill. Arrangement of the Ommatidia 60 8. In Stomatopoda .. . . 104 
IV. Structure of the Ommatidia. . 66 9, In Decapoda;; . . .. - . 108 
1. In Amphipoda .... . 68 V. Ommatidial Formule . . . 115 
Sin Phyllopoda .-. 9. - . 3) VL Innervation of the Retina. . 116 
S. In' Copepoda...) 2) at. Sa VIE Theoretic Conclusions . . . 118 
4, InIsopoda ... . . . 84|VIIL Bibliography .- +--+. - 131 
&. InLeptostraca . . . . . 98] IX Explanation of Figures. . . 141 
INTRODUCTION. 
Some four years ago, at the suggestion of my instructor, Dr. E. L. 
Mark, I began the investigation of the compound eyes in Crustaceans. 
In order to familiarize myself with the subject, I determined to study 
at first in detail the structure of the eyes in a single species, and for 
this purpose I turned my attention to our common lobster, Homarus 
americanus. My results were published in a paper entitled “The His- 
tology and Development of the Eye in the Lobster.” Since the publica- 
tion of that paper, I have had the opportunity of examining the eyes in — 
a number of other Crustaceans, and my observations and conclusions 
concerning these eyes are contained in the following pages. 
The material which I have used in the present study was in part sup- 
plied to me through the kindness of several friends, and in part collected 
by myself. Of that which I obtained myself, some was gathered in 
the immediate vicinity of Cambridge, but much of it came either from 
Wood’s Holl, Mass., or from Newport, R. I. The material which I 
obtained at Newport was collected at the Newport Marine Laboratory 
during the summer of 1890, and consisted of specimens of Idotea, 
Evadue, and Pontella ; that which I got at Wood’s Holl was collected 
at the United States Fish Commission Station during a brief period 
1 Contributions from the Zodlogical Laboratory of the.Museum of Comparative 
Zodlogy, under the direction of E. L. Mark, No. XXV. - 
VOL, XXI. — NO. 2, ~~ goniat } che 
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