OF MULE S. 31 



jfind female afs. It is the number of conformi- 

 ties and diflimilarities which conftitutes or diftin- 

 ^uiflies fpecies ; and, fince the fpecies of the afs 

 .has at all times been feparatcd from that of the 

 horfe, it is apparent, that, by mixing thefe two 

 fpecies, whether by means of females or males, 

 we diminifli the number of conformities which 

 conftitute the fpecies. Hence the males will en- 

 gender and the females produce feldomer, and 

 with more difficulty ; and even thofe mixed fpe- 

 cies, if their conformities were fewer, would be-" 

 come entirely barren. Mules of every kind, 

 therefore, mull be rare ; becaufe it is only by 

 being deprived of its natural female, that any a- 

 nimal will iuterjnix with a female of a different 

 fpecies. Even when mongrel animals approach 

 each other with fome degree of warmth, their 

 produce is neither fo certain nor fo frequent as 

 in pure fpecies, where the number of conformi- 

 ties is greater. Now, the produce of mixed fpe- 

 cies will be lefs frequent, in proportion to the 

 infecundity of the pure fpecies from whom they 

 proceed ; and the produce of animals proceed- 

 ing from mixed fpecies will always diminifli in 

 proportion as they recede from the original ftock; 

 becaufe the conformities between them and any 

 Other animal are augmented. For example, I 

 am perfuaded, from the reafons above affigned, 

 that an intercourfe between two bardeaux would 

 be abortive. Befides, thefe animals proceed from 

 two fpecies which are not very fertile, and are 



alfo 



