OF ARTS AND SCIENCES. 179 



present time, he added, an equal knowledge of all the facts in 

 Botany and Zoology. 



Professor Agassiz referred to his former statements with 

 regard to the similarity of the turtles of Eastern Asia and 

 Eastern North America, and of those of Western North 

 America and Europe, and showed how these differences 

 seemed to be related to the geological age of these respec- 

 tive regions, and were at variance with the supposition of 

 an interchange of species, such as Professor Gray believes to 

 have occurred in the vegetable world : in the instance quoted, 

 there is an alternation of two fields of animal life of entirely 

 different types. In conclusion Professor Agassiz reiterated 

 his statement, that he believed that the present races of ani- 

 mals were originally created on the earth in about the same 

 proportionate numbers as they are found to have at the pres- 

 ent time, and in about the same localities as those they now 

 occupy. 



Professor Peirce spoke of the changes of temperature which 

 had been referred to as having influenced the distribution of 

 plants and animals, and said he thought it an important in- 

 quiry, to discover how such a change could have taken place. 

 With regard to the supposed cooling down of the earth, he 

 showed that the conditions under which it could have taken 

 place were inconsistent with the existence of plants and ani- 

 mals on its surface, and the time when it must have occurred 

 must have been long before they were created. The sun's 

 temperature, he said, might have undergone changes from time 

 to time, but there was no proof that such had been the case ; 

 and if it had been so, the eflect on the earth would have been 

 uniform. The change of the area of the land, and the eleva- 

 tion of portions of the earth's surface, would account for the 

 glacial period, and climatic and meteorological changes might 

 have resulted from changes in the amount of the earth's at- 

 mosphere. 



