OF ARTS AND SCIENCES. 181 



as it returned, while the rotation served to reduce the irregular 

 form to that of a circle. The joint action and resolution of 

 the forces thus brought into play might, Professor Horsford 

 conceived, account for the phenomenon observed. 



Further observations on the topic were made by the Presi- 

 dent and Mr. Hayes. 



Professor Horsford likewise gave an account of the phe- 

 nomena attending the death of a bear from strychnine, admin- 

 istered for the purpose by Professor Agassiz. Rapid decom- 

 position commenced almost immediately after death. 



Professor Agassiz gave a paper on the development of the 

 ova in insects. His observations were made by following 

 the tubular ovary of a species of Acheta, through the portion 

 charged with ova in different stages up towards its termina- 

 tion, where it contains simple structural cells. Some of the 

 latter merely take a further and special development, and be- 

 come ova. 



Three hundred and twenty-fourth meeting. 



November 13, 1S49. — Quarterly Meeting. 



The President in the chair. 



Mr. James D. Dana, through the Corresponding Secretary, 

 presented a copy of his work. The Geology of the United 

 States Exploring Expedition. 



Mr. E. C. Cabot exhibited plans of the former and present 

 wooden dams across the Connecticut River at Hadley, and 

 explained the different principles on which they were con- 

 structed. 



Professor Agassiz made a verbal communication, to show 

 that, throughout all classes of the animal kingdom, there is 

 such a direct relation between the structure of animals and 

 the element in which they dwell, that the circumstance of 

 habitat will go far towards determining the relative systematic 

 position of groups and species; the marine animals ranking 

 lowest, those of fresh water next, and the land animals high- 

 est : also, that the series so formed corresponds to the order of 

 appearance in time. 



