i58 LAWS OF MULTIPLICATION. 



shall have a generous diet. Respecting Pigeons Macgillivray 

 writes : — " that their breeding depends much on their 

 having plenty of food to fatten them, seems, I think, 

 evident from the circumstance that, when tamed, which 

 they easily are, they are observed to breed in every month of 

 the year. I do not mean that the same pair will breed every 

 month ; but some in the flock, if well fed, will breed at any 

 season." There may be added a fact of like meaning 



which partially- domesticated birds yield. The Sparrow is one 

 of the Finch tribe that has taken to the neighbourhood of 

 houses; and by its boldness secures food not available to its 

 congeners. The result is that it has several broods in a sea- 

 son, while its field-haunting kindred have none of them more 

 than two broods, and some have only one. 



Equally clear proof that abundant nutriment raises the rate 

 of multiplication, occurs among Mammals. Compare the 

 litters of the Dog with the litters of the Wolf and the Fox* 

 Whereas those of the one range in number from 6 to 14, the 

 others contain respectively 5 or 6 or occasionally 7, and 

 4 or 5 or rarely 6, Again, the wild Oat has 4 or 5 kittens ; 

 but the tame Cat has 5 or 6 kittens 2 or 3 times a-year. 

 So, too, is it with the Weasel tribe. The Stoat has 5 

 young ones once a-year. The Ferret has 2 litters yearly, 

 each containing from 6 to 9 ; and this notwithstanding that 

 it is the larger of the two. Perhaps the most striking 

 contrast is that between the wild and tame varieties of 

 the Pig. While the one produces, according to its age, from 

 4 to 8 or 10 young ones, once a year, the other produces 

 sometimes as many as 17 in a litter ; or, in other cases, will 

 bring up 5 litters of 10 each in two years — a rate of reproduc- 

 tion that is unparalleled in animals of as large a size. 

 And let us not omit to note that this excessive fertility 

 occurs where there is the greatest inactivity — where there is 

 plenty to eat and nothing to do. There is 



no less distinct evidence that among domesticated Mammals 

 themselves, the well-fed individuals are more prolific than 



