304 PROCEEDINGS OF THE ACADEMY OF [1884. 



the gastropod e^^e, the former in Fusus, and the latter in Murex. 

 I have carefully investigated the embryological growth of this 

 same organ in Nassa, and lastl}^ Carriere^ gives an account of 

 the regenei'ation of the eye after amputation in the Pulmonata. 



We find that ontogen}' merely recapitulates phj-logeny, as we 

 would naturally anticipate. There is first an invagination, which 

 closing forms a sphere ; in the cells of this invagination there 

 is a deposit of pigment, and from them a cuticular lens is formed, 

 which increases in size by the addition of concentric layers. A 

 nerve is there developed and connects this eye with the superior 

 cephalic ganglia. 



We will now pass to consideration of the eyes of the vertebrata, 

 which, with a few exceptions, are remarkable for the similarity 

 in general plan of organization throughout the whole group. 



1 will not enter here into a detailed account of the work that 

 has been done on this subject, nor into a description of the finer 

 anatomy, except where necessary to illustrate points under con- 

 sideration. I leave these to a future and more exhaustive work 

 upon the "Anatomical and Physiological Evolution of the Organ 

 of Vision," upon which my friend. Dr. Charles A. Oliver, and 

 myself are now engaged, and which is to appear under our joint 

 names. 



The general structure of the eye of the vertebrata is well known, 

 and I will here simply draw attention, to some of the cardinal 

 points. 



The eye consists of a more or less spherical body, bounded in 

 front by a transparent plate, the cornea, which is a continuation 

 of the white opaque enveloping sheath of the eye-ball, called the 

 sclerotica. Internal to this sclerotica is a layer of pigment 

 (choro'idea), passing forward to about the position of the junction 

 of the cornea and sclerotica, and also extending over the posterior 

 wall of the iris. Lying on this pigmented layer is the retina, the 

 sensory portion of which is considered to be a continuation of 

 the optic nerve, and which passes beyond the equator of the eye 

 to a point called the ora serrata. The cavity of the e3'e-ball is 

 divided anterio-posteriorly into two. principal chambers, the 

 anterior one is again subdivided into two, called the anterior 

 and the posterior chamber, and includes all the space anterior to 



^ Carriere, Jus., Studien iiber die Regenerationseischeinungen bei den 

 Wiibellosen. I. Die Regeneration bei den Puhnonaten. Wiirzburg, 1880. 



