Proceedings of the Microscopical Society. 415 



Uie Armadillos j after explaining the well-marked differences in the mi- 

 croscopic characters of the dental structure in these two families of the 

 so-called Edentata, Mr Owen proceeded to describe the structure of the 

 teeth of the megatherium, and to shew that in its close resemblance to 

 the dental structure of the sloths, it confimied the views of the great foun- 

 der of the science of fossil remains. This paper was accompanied by a 

 number of very beautiful illustrative drawings, exhibiting the minute struc- 

 ture of the teeth of the animals referred to. 



• ^ Mr Jackson then read a short paper, drawing the attention of the So- 

 ciety to a mode of mounting the compound microscope, which differs in 

 some particulars from the methods generally adopted. The principal ob- 

 ject to be kept in view in the construction of the instrument, is the pre- 

 vention of those accidental vibrations which so much interfere with mi- 

 croscopic examinations, especially in the neighbourhood of crowded tho- 

 rough-fares. This object is effected by connecting together the body and 

 Stage of the instrument in such a manner, that whatever vibrations are 

 communicated to the one shall be equally comnuinicated to the other. 

 In the instrument of Mr Jackson this principle has been carried further 

 than has hitherto been effected ; and it also affords improved facilities for 

 mmutc adjustments, and the accurate admeasurement of microscopic ob- 

 jects. 



A discussion ensued on the subject of Mr Jackson's paper, and also on 

 the best methods of measuring microscopic objects, and the greater diffi- 

 culties encountered in ascertaining the antero-posterior diameters of mi- 

 nute bodies, as compared with the facilities whith we possess of obtain- 

 ing lateral measurements. The meeting then resolved itself into a con- 

 versazione, during which a number of interesting objects were exhibited 

 by individual members, many of whom had their microscopes upon the 

 table. 



The meeting adjourned at 11 o'clock. 



Wednesday, February 10. 1840, R. H. Solly, Esq. in the Chair.— A pa- 

 per was read by Jlr Quekett, on the development of the vascular tissue 

 of plants, in which it was shewn that the membranous tube of vessels 

 originated from a cytoblast iu a manner similar to that described by 

 Schleidcn in the formation of cells/"- from which at first it is difficult to 

 recognise them; but in a short time they assume a very elongated form, 

 and the cytoblast disappears. Before the fibre is deposited, the contents, 

 which are gelatinous, are crowded with numerous most minute granules, 

 which possess the motion known as that of " active molecules," and after 

 a short time when they have become a little enlarged, they adhere to the 

 inner surface of the tube containhig tiiem in a different manner for each 

 Tcsscl, so that the scvcnd varieties of vascular tissue arc not degenera- 

 tions of each other, but are each constructed originally on the plan they 

 arc always observed to present to tiie eye. 



* See Taylor's Scientific Memoirs, vol. ii. p. 2.91, 



