247 



Five jars containing Reptiles, Insects, &c. were pre- 

 sented in the name of Mr. A. F. Preston. 



The thanks of the Society were voted for the donation. 



September 1, 1852. 



Dr. Durkee in the Chair. 



Dr. Burnett read a paper on the Crystalhne Lens and its 

 formation. After reviewing the opinions of previous ana- 

 tomists on this subject, he gave the results of his own in- 

 vestigations as follows : — 



1. In the Mammalian Vertebrates. In the embryo goat 

 of two months, the crystalline lens is biconvex and made up of 

 three parabolse, the convexities of which point to the centre, 

 leaving there a central triangular space. The central portion of 

 the lens, extending to near the circumference, is opaque; and 

 the opacity is most marked at the very centre. 



The central portion is composed of minute utricles, which 

 towards the circumference are seen to increase in size, until, on 

 the border of the opacity, they appear as quite sizable vesicles, 

 some of which are nucleated, in fact, are cells. Thus there 

 exists in this opaque central portion an appearance of all the 

 transitionary stages of minute utricles to large vesicles and 

 cells, and this development has resulted from a mere expansion 

 of these utricles, and not by the Schwann mode of cell-forma- 

 tion. 



At the junction of the opaque portion with the clear border, 

 there is perceived a tendency of the cells to arrange themselves 

 into rows or serial, longitudinal groups, which rows are parallel 

 with the long diameter of the parabola. Then, by the coales- 

 cence of these rows of cells, tubes are formed, and from these, 

 fibres. Thus these fibre tubes have their origin not by the elon- 

 gation of single cells, as Schwann had supposed, but by the 



