THK " sax UAL SEASON OF MAMMALS. 6 



animals wlieu they should not be so used, the sanae terms are 

 used foi- different processes and conditions iu female mam- 

 malsj and it is necessary for a clear understanding of the 

 subject that the limits of their use should be detinedj and 

 where needful new terms adopted. 



One of tiie most fertile sources of confusion is^ disregard 

 of the fact that the history of the generative phenomena 

 exhibited by female mammals is different when reproduc- 

 tion takes place and when it does not take place ; it is 

 essential that this fact should be kept in mind. 



The remainder of this Introduction I have devoted to a 

 definition of the terms used in the following pages^ and to an 

 endeavour to show wherein they differ or are in accord with 

 those now in use. 



Reproductive Period. — I have used this expression to 

 denote the whole of that period in the life of a mammal, 

 whether male or female, during which its generative organs 

 are capable of the reproductive function ; and in contrast to 

 the Pre-reproductive and Post-reproductive periods 

 which severally precede and follow it, during which the gene- 

 rative organs are either not fully developed or are degenerate. 



Ilie bearing of young, however, is not possible at all times 

 during the reproductive period. In the course of that period 

 there are intervals during which the generative organs of all 

 mammals exhibit, on the one hand special activity, and on 

 tlie other hand a fallow condition. This variation is periodic, 

 and is due, not to a periodic degeneration from a stable con- 

 dition, but to the periodic accession of a special stimulus, 

 culminating in sexual desire, and resulting in coition and in 

 gestation in the female when conception takes place. 



The periodicity of this stimulus is very variable, and is 

 influenced by many factors of both extraneous and internal 

 origin. 



Breeding Season is adopted to denote the whole of that 

 consecutive period during which any male or female mammal 

 is concerned in the production of young, and it is not appli- 

 cable to any isolated portion of that period. 



