308 Proceedings of Philosophical Societies. [Apuil, 



The ground on which the painting was executed was powdered 

 marble, cemented with lime, which was polished. No wax or 

 animal gluten was discovered on any of the paintings. 



March 9 and l(). — At these two meetings a paper was read from 

 Dr. Brewster, on the laws which regulate the polarization of light 

 bv reflection from th.e second surfaces of transparent bodies. 



LINNJEAN SOCIEXy. 



At the meeting of the 7th March a paper was read from Mr, 

 Sowerby, on a branched fossil found in Green Sand, War- 

 minster, to which he proposes to give the name of pedunculum 

 lobatnm. A figure was also exhibited. 



At the same meeting a paper was read from the Rev. Patrick 

 Keith on the epidermis of plants, in which, after stating the gene- 

 ral analogy pointed out by Grew, and other early vegetable pliysio- 

 loi-ists, between the epidermis of plants and animals, he examines 

 the doctrine especially supported by M. Mirbel, who regards that 

 substance as merely the external surface of the parenchyma acted 

 upon and hardened by the atmosphere. He then shows that this 

 last opinion is unfounded, and finally endeavours to establish the 

 general analogy adopted by the early writers. 



A memoir from Dr. Leach on the distribution of the orders com- 

 posing the class Insecta, with descriptions of some new genera and 

 species was read. In the following table an outline of his classifi- 

 cation is inserted. 



CLASS INSECTA. 



Subclass I. — ametabolia. 



Insects undergoing no metamorphoses. 



Order I. Thysanura. — Tail armed with setae. 

 Order II. Anoplura. — Tail without setae. 



Subclass II. — metabolia. 



Insects undergoing metamorphoses. 



Century I. Elythroptera. — Insects with elytra. 



Odontostoma. — Mouth with mandibles. 

 * Metamorphoses incomplete. 

 Order III. Coleoptera. — Wings transversely folded j elytra crus- 

 taceous, covering the wings, with the suture strait. 

 ** Metamorphosis nearly coarctate. 

 Order IV. Strepsiptera. — Wings longitudinally folded; elytra 

 coriaceous, not covering the wings. 



*** Metamorphoses semi-complete. 

 Order V. Dermaptera. — Wings longitudinally and transversely 

 folded ; elvtra somewhat crnstaceous, abbreviated, with the suture 

 strait. 



Order VI. Orthoptera. — Wings longitudinally folded ; the in- 

 ternal margin of one elytron covering the same part of the other ; 

 elytrfi coriaceous. 



