PROCEEDINGS OF SOCIETIES. 43 



tions or medical school, and addresses, to Mr. T. C. White, 32, Belgrave 

 Fioad, Pimlico, S.W., or to Mr. J. W. Groves, St. Bartholomew's 

 Hospital, Smithfield, E.C. 



The next meeting, of which clue notice will be given, will take 

 place on the third Friday in January. 



Brighton and Sussex Natural History Society. 



October 24th. — Microscopical Meeting. Mr. G. Scott, President, 

 in the chair. Dr. Hallifax on " The Invertebrate Eye." 



When asked to introduce the subject of the invertebrate eye, 

 between which and the vertebrate were great points of dissimilarity, 

 he felt, from having made sections for the microscope of the eyes of 

 insects and crustaceans, he might be able to direct the minds of 

 some of his hearers to, not simply an admiration of a beautiful object, 

 but the establishing a principle, which should guide all inquiry, viz. 

 the tracing out a unity of plan where there appeared to be diversity 

 of structure. Whatever organ we investigated in any class of the 

 animal creation should be compared with the same organ in other 

 classes, in order to show their connection by some general plan of 

 unity. As an example of what might be deduced by comparison, he 

 might mention what Mr. Wonfor had proved. He found certain 

 scales, called battledores and plumules, only on the males of certain 

 butterflies, and pursuing the plan of comparison, he had arrived at 

 a general law that any butterfly on which such scales were found was 

 invariably a male. 



Newton, who brought the seemingly chaotic mass of stellar and 

 planetary matter not only into order, but simplified their movements 

 under mathematical laws, believed that the seeming chaos of the 

 animal and vegetable kingdom would in time be reduced to harmony. 

 This was before Cuvier, Linnteus, and others had brought about our 

 present classification. It was always a great incentive to inquiry, 

 when we saw any organ devoted to the same evident purpose but 

 differing in structure, to endeavour to bring it in harmony with some 

 general law of unity of plan. 



In the invertebrates, taking the eye of the dragon-fly as a type, 

 was an apparent divergence, as wide as possible from the highest 

 type of the vertebrates, the human eye. Comparing them, we found 

 in the first a great mass of optic ganglia, proceeding from the cephalic 

 ganglia (the equivalent of brain in the vertebrates), subdivided and 

 covered with pigment, giving off nervous matter, covered also with 

 dark pigment, changing into a transparent substance terminating in 

 a curved surface, which abutted on a cornea composed of numerous 

 facets, 4, 5, and 6 sided, but each consisting of a lens, convex ex- 

 ternally and internally. Each of these facets, or convex lenses, was 

 capable of bringing the rays of light to a focus upon the transparent 

 pigment-covered substance, consisting of transformed nerve matter. 

 In the vertebrate eye we had a globe filled with vitreous matter, a 

 crystalline lens and aqueous matter, refracting the rays of light and 

 causing them to fall on the nervous matter, called the retina, lining 

 the interior of the globe. The nervous expansion of the retina was 



