160 



geal ganglia in the Lamellibranchiata appear homologous with those 

 of Doris, 



Having determined the existence of a true sympathetic or organic 

 nervous system in Doris, the authors feel themselves more in a 

 position to trace a parallelism betvi^een the oesophageal nervous 

 centres of these Mollusca and the cerebro-spinal system of the Ver- 

 tebrata, and accordingly they find there is a strict analogy between 

 them, even to the individual pairs of ganglia of which they re- 

 spectively consist, the general result being that the whole of the 

 ganglia, grouped around the oesophagus in these Mollusca, answers 

 to the encephalon, and a small portion of the enrachidion, of the 

 Vertebrata. 



Organs of the Senses. — The auditory capsules are microscopic, 

 composed of two concentric vesicles, the inner enclosing numerous, 

 oval, nucleated otolithes. The eyes are minute black dots, beneath 

 the skin, attached by a pedicle to a small ganglion. They are 

 made up of a cup of pigment, receiving from behind the nerve, and 

 lodging in front a lens, having in advance of it a cornea, the whole 

 enclosed by a fine capsule. The authors believe they have shown 

 the dorsal tentacles to be the olfactory organs. 



The organs of touch are, the general surface of the skin, but 

 more particularly the oral tentacles or veil. Taste is most probably 

 located in the lips and channel of the mouth, the tongue being a 

 prehensile organ, and ill-adapted as the seat of such a function. 



In conclusion, the authors comment on the high organization of 

 the Dorida, and express their belief that the genus, as at present 

 understood, will require to be broken up into several groups. 



March 11, 1852. 

 THE EARL OF ROSSE, President, in the Chair. 

 The following papers were read : — 



1. "Remarks on certain points in Experiments on the Dififrac- 

 tion of Light." By the Rev. Baden Powell, M.A., F.R.S. &c., 

 Savilian Professor of Geometry in the University of Oxford. Re- 

 ceived Nov. 10, 1851. 



The chief object of this communication was to examine into the 

 experimental evidence adduced in a recent paper by Lord Brougham 

 (Phil. Trans., 1850, Part I.), without at all entering on the question 

 of the peculiar theory therein proposed, solely with the view of in- 

 quiring how far the actual new facts adduced, when simply stated 

 and divested of the peculiar theoretical language in v/hich they are 

 delivered, do or do not militate against the undulatory theory. 



The author had devoted a portion of the summer to a careful 

 repetition of all the chief experiments described in the paper referred 

 to, in some of which, however, he had been unable to reproduce the 

 Jesuits described. After referring to the preliminary experiments 



