416 Royal Society. 
the character of a specific stimulus. The author found that the 
most intense artificial light that he could obtain from incandescent 
lime produced no sensible effect on plants. 
The latter part of the paper is occupied by details of the experi- 
ments which the author made with a view to ascertain the action of 
plants upon the atmosphere, and more especially to determine the 
proportion that exists between the effects attributable to their action 
during the night and during the day; and also the proportion be- 
tween the carbonic acid absorbed, and the oxygen evolved. 
His experiments appear to show that at least 18 per cent. of oxy- 
gen may be added to the air confined in a jar by the influence of a 
plant contained within it. He also infers that the stage of vegetable 
life at which the function of purifying the air ceases, is that in which 
leaves cease to exist. The author shows that this function is per- 
formed both in dicotyledonous and in monocotyledonous plants, in 
evergreens as well as in those that are deciduous, in terrestrial and 
in aquatic plants, in the green parts of esculents as well as in ordinary 
leaves, in Alge and in Ferns as well as in Phanerogamous families. 
Professor Marcet has shown that it does not take place in Fungi*. 
The reading of a paper, entitled, ‘« On the Anatomical and Optical 
Structure of the Crystalline Lenses of Animals, being the continua- 
tion of the paper published in the Philosophical Transactions for 
1833.” By Sir David Brewster, K.H., LL.D., F.R.S.,—was com- 
menced. 
Jan, 21.—Sir David Brewster’s paper, entitled, “On the Anato- 
mical and Optical Structure of the Crystalline Lenses of Animals, 
being the continuation of the paper published in the Philosophical 
Transactions for 1833,” + was resumed and concluded. 
The author has examined the structure of the crystalline lens of 
the eye of a great variety of animals belonging to each of the four 
classes of Vertebrata; and has communicated in this paper a de- 
tailed account of his observations, arranged according as they re- 
late to structures more and more complex. In a former paper, 
published in the Philosophical Transactions for 1833, the lens of the 
Cod fish was taken as the type of the simplest of these structures, in 
as muchas all the fibres of which it is composed converge, like the 
meridians of a globe, to two opposite points, or poles, of a spheroid 
or lenticular solid ; both of which poles are situated in the axis of 
vision. The structure which ranks next in respect of simplicity is 
that exhibited in the Salmon, among fishes; in the Gecko, among 
reptiles; and in the Hare, among Mammalia. It presents at each pole 
two septa placed in one continuous line, in different points of which 
all the fibres proceeding from the one surface to the other have their 
origin and termination. A structure somewhat more complex is 
met with in the lenses of most of the Mammalia, and is particularly 
exemplified in the lion, the tiger, the horse, and the ox. Three 
septa occur at each pole in the form of diverging lines inclined to 
* A notice of the results obtained by Prof. Marcet will he found at p. 82 
of the present volume.—Enpir. 
+ Sir D. Brewster’s former paper on this subject was given entire, with 
additions, in our Number for March last, p. 193.—Epir. 
