326 THEOltY OF THE SYSTEM. . 222. 



The transitions arise from the series of characters. Simple 

 transitions take place only in one character, compound transi- 

 tions in more than one character at the same time. The 

 simple transitions are very evident, but comparatively rare. 

 The compound ones are more common, but they must be fol- 

 lowed up in every simple transition of which they consist, 

 if we wish to draw consequences upon which we may rely. 

 This is effected by supposing the differences in all the pro- 

 perties to disappear, except in the single one, in which the 

 transition is to be considered. If these differences consti- 

 tute members of one and the same series, there exists a 

 transition in this property ; if they cannot be joined in one 

 and the same series, we are not entitled to assume a transition. 

 After having thus followed up and demonstrated the simple 

 transitions in every one of those properties which present 

 differences in a number of individuals, we may consider 

 the compound transition, with the greatest security, as 

 really existing, and the individuals themselves as passing 

 into each other. 



. 222. HOMOGENEITY FROM THE TRANSITIONS. 



Individuals, connected by transitions, are homo- 

 geneous, or belong to one and the same species. 



A transition in a single character, for instance in the 

 forms of crystallisation, arises, if these forms of the indi- 

 viduals are members of the same series of crystallisation ^ 

 all the remaining properties being equal. Under these cir- 

 cumstances the individuals are homogeneous. 



The colours form a transition, if, in several individuals, 

 exactly agreeing in the rest of their characters, they repre- 

 sent members of the same series of colours. But in this 

 case again the individuals are homogeneous. 



Hence the individuals also are homogeneous, if they are 

 joined by compound transitions. 



It is not necessary that the members of the series of 

 crystallisation representing the transition, be such as im- 



