THE STRUGGLE FOR EXISTENCE 21 



be capable of preserving one pair, and not more than 

 one pair, to succeed their parents in a generation. 



" I had thus two distinct problems before me, first to 

 discover what is Nature's method of eliminating her 

 excess of reproduction, and second, what is her method 

 of preserving alive the necessary and no more than the 

 necessary number of young to take the place of their 

 parents. For a time the solution of the first problem 

 appeared to me a hopeless task ; but a seemingly 

 accidental circumstance put me on a track that 

 eventually brought me to the required solution. For 

 some years I had kept in my house two cats, a male 

 and a female. From time to time in the course of 

 four years the female showed signs of pregnancy, and 

 then appeared lean and lank, as if she had been newly 

 delivered ; but no brood ever appeared to certify the 

 fact. The male, however, happening to be killed, the 

 female not long after became a happy mother of 

 kittens. It was therefore obvious that the male had 

 devoured her former litters. More in jest than 

 earnest, I asked myself, Can this be the manner in 

 which Nature's excess of reproduction in respect of 

 the carnivora is eliminated ? However, my curiosity 

 on the subject was excited, and I made further 

 inquiries and observations. I found that in every 

 case where a tomcat was tenant of the same house 

 with a tabby, the litters of the latter were sure to be 

 devoured by the former. I have also more than once 

 observed, and have been informed by others who 

 have noticed it, that when the female is pregnant, the 



