338 Royal Society. 



tion of two hemispheres of glass closely joined together at their 

 bases, so as to form an air-tight globular receptacle for the plant 

 subjected to experiment. 



The general conclusions he deduces from his numerous experi- 

 ments conducted during several years, are, first, that in leaves which 

 are in a state of vigorous health, vegetation is always operating to 

 restore the surrounding atmospheric air to its natural condition, by 

 the absorption of carbonic acid and the disengagement of oxygenous 

 gas : that this action is promoted by the influence of light, but that 

 it continues to be exerted, although more slowly, even in the dark. 

 Secondly, that carbonic acid is never disengaged during the healthy 

 condition of the leaf. Thirdly, that the fluid so abundantly exhaled 

 by plants in their vegetation is pure water, and contains no trace of 

 carbonic acid. Fourthly, that the first portions of carbonic acid 

 gas contained in an artificial atmosphere, are taken up with more 

 avidity by plants than the remaining portions ; as if their appetite 

 for that pabulum had diminished by satiety. 



" On the minute structure of the Skeletons, or hard parts of Inver- 

 tebrata." By W. B. Carpenter, M.D. Part II. " On the structure of 

 the Shell in the several families and genera of Mollusca." 



The author here gives in detail the results of his inquiries into 

 the combinations of the component elements of shell as they are 

 met with in the several families and genera of the Mollusca ; and 

 considers all these results as tending to establish the general propo- 

 sition, that where a recognizable diversity presents itself in the ele- 

 mentary structure of the shell, in diflTerent groups, that diversity af- 

 fords characters which indicate the natural affinities of the several 

 genera included in those groups, and which may therefore be em- 

 ployed with advantage in classification, and in the recognition and 

 determination of fossils. 



June 15. — " On the supposed developement of the Animal Tissues 

 from Cells." By James Stark, M.D., F.R.S.E. 



The author controverts the prevailing theory of the developement 

 of animal tissues from cells, and denies the accuracy of the micro- 

 scopical observations on which that theory is founded, as regards the 

 anatomy of the adult as well as of the fcBtal tissues. He asserts that 

 at no period of foetal life can rows of cells be discovered in the act 

 of transformation into muscular fibres: and he denies that these 

 fibres increase either in length or in thickness by the deposition of 

 new cells. He contends that the ultimate filaments of muscles, as 

 well as all the other tissues of the body, are formed from the fibri- 

 nous portion of the blood, which is itself composed of globules that 

 are disposed to cohere together, either in a linear series, so as to 

 form a net- work of fine filaments, or in aggregated masses of a form 

 more or less globular, composing what have been termed fibrinous 

 corpuscles. These corpuscles have been considered to be the nuclei 

 of cells ; but the author regards them as being merely accidental 

 fragments of broken down tissues, adhering to the filaments, and 

 noways concerned in their developement. The more regularly dis- 

 posed granules, which are observed to occupy the spaces intervening 



