THE BEGINNINGS OF LIFE. 21 



in 1837, M. Boussingault, after contrasting the meteor- 

 ological circumstances in which wheat, barley, Indian 

 corn, and the potato are developed at the equator and 

 in the temperate zones, with their different rates of 

 growth in these situations, came to the conclusion c that 

 the same annual plant everywhere receives the same 

 quantity of heat in the course of its existence.' And 

 in one of his more recent works, speaking of the Fora- 

 minifera, Dr. Carpenter says 1 , c We have found strong 

 reason for regarding temperature as exerting a most im- 

 portant influence in favouring, not merely increase in 

 size, but specialization of development: all the most 

 complicated and specialized forms at present known 

 being denizens either of tropical or sub-tropical seas, and 

 many of these being represented in the seas of colder 

 regions by comparatively insignificant examples which 

 there seems adequate reason for regarding as of the 

 same specific types with the tropical forms, even though 

 deficient in some of their apparently most important 

 features/ That the rate of growth in plants depends 

 most notably upon the amount of light and heat to 

 which they are subjected is a fact familiar to most of 

 us. The stimulation of the vital processes by heat is, 

 indeed, most easy of demonstration in some cases. It 

 is now perfectly well known that in Valisneria^ Chara^ 

 Anacharls^ and other plants in the cells of which there 

 is a well-marked cyclosis, the rate of revolution of the 



1 'Introduction to the Study of the Foraminifera ' (Ray Soc.), 1862, 

 p. 9. 



