178 Instinct. 



the question naturally arises, How far, and under 

 what conditions is it subject to variation ? 



There is a tendency in almost all plants and an- 

 imals, if not in all, to vary from one exact type, 

 giving rise to varieties. The extent to which this 

 variation may go, is at present one of the disputed 

 points among naturalists, and one which it is very 

 difficult to settle. All readily acknowledge that 

 species vary so as to give a multitude of varie- 

 ties ; as in the case of the common apple and oth- 

 er cultivated fruits; while some hold to the dis- 

 tinct origin of species themselves, and others re- 

 gard them as simply permanent, well marked va- 

 rieties. 



Without entering into this discussion fully, 

 which our present purpose does not require, there 

 are certain things in regard to this variation of 

 species, upon which most naturalists seem to be 

 agreed. 



1. Variation may take place in any plant or an- 

 imal in a manner and from causes quite beyond 

 our comprehension ; that is, apparently from some 

 original constitution of the being. 



2. Rapid variation is in general, most common 

 among the higher groups of plants and animals; 

 especially among those most useful to man. 



3. When the process of variation has com- 

 menced in any kind, we naturally expect from our 

 observation, that instances of variation in that kind 

 will become increasingly common. 



This may explain the reason for our finding so 

 much variation among our best cultivated plants 



