288 RAYMOND PEARL 



Suppose some deleterious agent, such as alcohol, to act upon 

 the germ cell population X with an intensity P, the value of P 

 being less than that required to kill all the germ cells at once. 

 It is a reasonable assumption in accordance with known physi- 

 ological laws that effect produced by the agent will be propor- 

 tioned to the initial distribution of physiological vigor among 

 the cells. The weakest germ cells will be killed, those a little 

 stronger will be severely injured and so on. It is legitimate 

 to assume that for values of the intensity factor P which are 

 below a certain level, say Pm there will be a certain proportion 

 of germ cells, which because of their high innate physiological 

 vigor are very resistant, will not be sensibly affected by the 

 harmful agent at all. The effect of the agent upon our funda- 

 mental gametic equation will be to introduce a new term. Using 



2 3 4 5 



Fig. 4 For explanation see text. 



primes throughout to indicate the conditions after the dele- 

 terious agent has acted we shall have this result — 



X' = A' + {a' + V) (ii) 



where A' denotes the number of germ cells which do not take 

 part in forming zygotes, (a' + h') denotes those germ cells which 

 do enter into zygote formation, a' being those physiologically 

 vigorous cells which are highly resistant, and form vigorous and 

 perfect zygotes, and h' denoting the less vigorous germ cells 

 which are injured, but not put entirely out of commission, by 

 the deleterious agent, and because of their injuries produce 

 defective offspring. 



The relations between these several parts of the germ cell 

 population before and after the action of a harmful agent are 

 of interest. It would seem probable that the following rela- 

 tions must hold finally. 



