51 



bark over ten feet thick) has been hollowed out by fire and other 

 means, to a shell of about four inches in thickness. A piece of 

 this wood Dr. Gray found to contain, on an average, forty-eight 

 annual layers to an inch ; the semidiameter at this point being 

 five feet two inches, (viz. at twenty-five feet from the ground.) 

 Supposing the tree increased in diameter at the same rate during 

 its whole life, there would be nearly three thousand annual lay- 

 ers ; but Dr. Gray, in consideration of the greater thickness of the 

 layers of a young tree, and from comparison of sections of the 

 so-called Cypress of the Southern States, Taxodium distichum, 

 (as given in detail in the Proceedings of the American Academy, 

 Vol. 3, p. 96,) assigns about two thousand years as its highest 

 probable age. 



This tree is nearly allied to the Redwood of California, Taxo- 

 dium sempervirens. Don, of late described under the new genus 

 Sequoia, which is now growing in England, and rarely in this 

 vicinity, where it is barely hardy. As we have now seeds of the 

 VVellingtonia, it is hoped that ere long we shall have some young 

 specimens of this gigantic conifer. 



Prof. Wyman communicated the results of his recent re- 

 searches upon the structure of the heart, and the physiology 

 of the respiration in the Menobranchus and Batrachians. 



The group of reptiles, known as Perennibranchiates, retain 

 the gills throughout life, associated with rudimentary lungs ; 

 there has been a question as to the structure of the heart in 

 this group, i. e. as to the existence of a single or double auricle. It 

 has been pretty well determined that the proteus has but one au- 

 ricle ; the axolotl of Mexico has been found likewise to have only 

 one auricle. Prof. Wyman had found the heart of the meno- 

 branchus provided with a single auricle and ventricle. 



It has long been well known, that Batrachian reptiles respire 

 partly by means of the skin, and this has been satisfactorily de- 

 termined by the experiments of Edwards and others. Prof. 

 Wyman had seen, in dissecting the vascular system of the frog, 

 after minute injection with coloring matter, that the branch of the 

 pulmonary artery described by Muller as going only to the occi- 

 put, actually sends all of its blood to the skin, a fact to which 

 attention has been recently called by Bernard. There are also 



