MUSEUM OF COMPAEATIVE ZOOLOGY. 77 



life appeared on the earth, this would give us a total of not more than 

 fifty million of years since the first appearance of life upon this globe. 

 To this must be added as the age of the globe whatever time mathe- 

 maticians think necessary to reduce the globe to a condition fit for 

 animal life from its primitive state. 



Cambridge, May 23, 1883. 



