148 PROCEEDINGS OF THE AMERICAN ACADEMY 



chart of the path of the orbits of the c(^ets, which is con- 

 clusive in its exhibition of the relation of the comets to the 

 solar system. 



Dr. .T. C. Warren and Dr. Channing continued a discussion 

 which commenced at the last meeting, on the comparative 

 merits and safety of ether and chloroform as anassthetic 

 agents. 



Three hundred and nineteenth meeting;. 



May 8, 1849. — Monthly Meeting. 



The President in the chair. 



The Corresponding Secretary presented a memoir from 

 William S. Sullivant, Esq., entitled " Contributions to the 

 Bryology and Hepaticology of the United States, Part II.," 

 comprising the descriptions of several new or little known 

 Musci and Hepatica3, illustrated by figures. 



Professor Agassiz gave a summary account of his investiga- 

 tions upon Medusae. He has ascertained that their body con- 

 sists entirely of cells, preserving in all the different systems of 

 organs their character as true cells, and nevertheless perform- 

 ing very different functions. He showed that there is a com- 

 plete system of bundles of elongated cells, arranged in longi- 

 tudinal and transverse series, acting as muscles, and disposed 

 in several layers, one being superficial and another lining the 

 inner surface of the disk in Discophoras, whilst some penetrate 

 at various depths the gelatinous mass. The nervous system 

 consists of a circular cord of oval cells, extending along the 

 lower margin of the disk, from one eye-speck to the other, 

 and forming a ganglion at the base of each. He also showed 

 that the digestive system is naturally distinct from the tubes 

 through which the digested food, mixed with water, is circu- 

 lated, though at times they communicate directly with each 

 other. This circulation — the arrangement of which he has 

 ascertained by artificial injection — is very complicated in 



