CHAPTER I 



THE BREEDING SEASON 



" To everything there is a season, and a time to every purpose under the 

 heaven." Ecclesiastcs iii. 1. 



" IT is well known that almost all animals, except Man, have a 

 stated season for the propagation of their species. Thus the 

 female cat receives the male in September, January, and May. 

 The she-wolf and fox in January ; the doe in September and 

 October. The spring and summer are the seasons appointed 

 for the amours of birds, and many species of fishes. The 

 immense tribe of insects have likewise a determinate time for 

 perpetuating their kind ; this is the fine part of the year, and 

 particularly in autumn and spring. The last-mentioned class 

 of beings is subject to a variation that is not observed in the 

 others. Unusual warmth or cold does not retard or forward 

 the conjunction of birds or quadrupeds ; but a late spring 

 delays the amours of insects, and an early one forwards them. 

 Thus it is observed that, in the same country, the insects on 

 the mountains are later than in the plains." 



The foregoing quotation from Spallanzani's "Dissertations," * 

 although not strictly accurate in all its statements, contains 

 a clear recognition of two fundamental facts which indeed have 

 been realised from the earliest times ; firstly, that the periods 

 of reproductive activity among the great majority of animals 

 (not to mention plants) occur rhythmically, the rhythm having a 

 close connection with the changes of the seasons ; and secondly, 

 that the reproductive rhythm is liable, to a greater or less 

 extent, to be disturbed or altered by climatic or other environ- 

 mental influences. And while there may be a basis of truth 

 for the statement that the periodicity of the breeding season 



1 Spallanzani, Dissertations relative to the Natural History of Animals and 

 Vegetables. Translated from the Italian, vol. ii., London, 1784. 



