xx THE INFLUENCE OF ENVIRONMENT 393 



of a greenhouse, as has been done for four years, the 

 parthenogenesis continues without break, no males 

 being born to enjoy the comforts of that environment. 



Periods of fasting occur in the life-history of many 

 animals, and these are very momentous and progressive 

 periods in the lives of some, for the tadpole fasts before 

 it becomes a frog, and the chrysalis before it becomes 

 a butterfly. Lack of food, however, may stunt develop- 

 ment, as w r e see every day in the streets of our towns. 



(c) Radiant Energy. Of the forms of radiant energy 

 which play upon the organism, we need take account 

 only of heat and light, for of electrical and magnetic 

 influence the few strange facts that we know do not 

 make us much wiser. 



We know that increased warmth hastens motion, the 

 development of embryos, and the advent of sexual 

 maturity. An Infusorian (Stylonichia) studied by Maupas 

 was seen to divide once a day at a temperature of 7 -10 

 C., twice at 10-15, thrice at 15-20, four times at 

 20-24, five times at 24-27 C. At the last tempera- 

 ture one Infusorian became in four days the ancestor of 

 a million, in six days of a billion, in seven days and a 

 half of 100 billions, weighing 100 kilogrammes. By 

 consummately patient experiments, Dallinger was able 

 to educate Monads which lived normally at a tempera- 

 ture of 65 Fahr., until they could flourish at 158 Fahr. 



Cold has generally a reverse action, checking activity, 

 producing coma and lifelessness, diminishing the rate of 

 development, tending to produce dwarf or larva-like forms. 

 Here we are dealing with direct physiological effects, and 

 the mode of operation is in part clear. Cold lessens the 

 rate of certain chemical processes (as in the inorganic 

 domain) ; the formation of nuclein bodies within the 

 cell is slowed ; this puts a drag on cell-division and 

 growth. The dense population of small animals in boreal 

 seas, for some types denser than in the tropics, has been 

 explained by Loeb as due to this slowing of life. There 

 are more generations living at the same time. It would 

 be interesting if we had data as to the rate of growth 

 in the eternal winter of the Deep Sea. 



