I2O Permanence and Evolution. 



find it impossible to reduce the hypothesis 

 to a form definite enough to be capable of 

 verification. First take the former. 



Organised beings are supposed to have a 

 tendency to vary from unknown causes in un- 

 known directions. This process may go on so 

 fast as to produce a form considered by com- 

 petent naturalists a good species in a few 

 centuries (Porto Santo rabbit), or even in a few 

 years (black-winged pea-fowl), or so slowly that 

 the amphioxus has not yet, through millions of 

 ages, entirely acquired all the characteristics 

 of a vertebrate animal. The same strain may 

 be benefited by developing in opposite direc- 

 tions, under slightly different circumstances, the 

 difference being imperceptible with any means 

 of observation that we can employ. The 

 modifications go on imperceptibly, and the 

 geological record is so imperfect, that no reliable 

 indications can be gathered from it. Unlimited 

 time is at our disposal, and the way in which 



