No. 1. — The Histology and Development of the Eye in the Lobster. 



By G. H. Parker. 1 



Table of Contents. 



I. Introduction 



Methods 



II. Histology* 



1. Corneal Hypodermis . . . 



2. Cone-cells 



3. Distal Retinulse . . . . 



4. Intercellular Spaces of the 



Retina ....... 



5. Proximal Retinulas . . . . 



Page 

 1 

 3 

 4 

 6 

 10 

 15 



19 



20 



Page 



6. Accessory Pigment-cells . . 25 



7. Innervation of Retina ... 26 



III. Development ....... 31 



1. Plan of the Eye 31 



2. Optic Nerve 43 



3. Differentiation of Ommatidia 45 



4. Types of Ommatidia ... 56 



IV. Bibliography 59 



V. Explanation of Figures ... 60 



Introduction. 



Through the kindness of Mr. Alexander Agassiz it was my privilege 

 to spend the greater part of the summer of 1887 at the Newport Marine 

 Laboratory. During the preceding winter I had been interested in the 

 structure of the eyes in Arthropods, especially in the inversion of the 

 retina in Arachnoids and my instructor, Dr. E. L. Mark, had called my 

 attention to the importance of ascertaining whether the retina in the 

 compound eyes of Crustaceans was inverted or not. At about this time 

 Kingsley ('86 a ) published his preliminary account of the development of 

 the compound eye of Crangon, and claimed that in this crustacean, as 

 in spiders, the retina was inverted. For reasons which I shall mention 

 in the course of this paper, Kingsley's account did not seem fully sat- 

 isfactory to me, and consequently I decided to study for myself the 

 development of the eye in a crustacean. My visit to the Newport 

 Laboratory offered an excellent opportunity to collect embryological 

 material for such a study. During August and September spawning 

 lobsters were easily obtained, and I therefore determined to study 

 the eye in the lobster, Homarus americanus, Edwards. A series of 

 lobsters' eggs were collected, and before leaving Newport my observa- 



1 Contributions from the Zoological Laboratory of the Museum of Comparative 

 Zoology, under the direction of E. L. Mark, No. XVII. 

 vol. xx. — no. 1. 1 



