The Eye and Optic Tract of Insects

The structure of the eyes of the Arthropoda has been, a favourite subject with morphologists for many years, and many beautiful monographs have been published detailing the results of the careful observations that have been made upon this subject. Until the last few years the observations stopped, short at the basilar membrane, and the tract lying between the percipient elements and the brain remained unknown. Of late years, however, several papers have appeared dealing with the optic tract and its relations to the eye proper, or ommateum (Lankester and Bourne), and as some of these have attempted to throw doubts upon what were formerly considered to be well-founded homologies, I have gathered together in this memoir some of the most interesting results of the researches I have been carrying on for the last two or three years with the hope of being able thereby to throw some light upon these obscure or disputed points. In order to make my memoir more complete I have carefully revised the structure of the ommateum. itself in Musca vomitoria, and I shall here give a detailed account of it based upon, my own observations before I proceed to describe the nervous elements which connect it with the brain.