664 Studies in the Tkeory of Descent. 



this at least according to Von Hartmann must 

 take place in each of the successive generations, 

 so that by this means, combined with heredity, 

 the useful variation becomes increased. But how 

 comes it that this "tendency to variation" coincides 

 with the existence of the model both in time and 

 place ? Can this be due to accident if the two 

 have not a common cause ? The upholders of a 

 directive power will certainly .not admit this ; so 

 that there remains only Leibnitz's assumption of a 

 pre-established harmony contained in the first or- 

 ganic germ, which, after innumerable transforma- 

 tions of the organic form and after millions of years, 

 gave rise in the midst of the Amazonian region to an 

 inedible Heliconide with certain yellow, black, and 

 white markings on the wings, and at precisely the 

 same time developed the tendency in a Pieride at 

 the same spot on the globe to imitate this Heli- 

 conide as a model ! 



In adddition to this assumption, which is 

 certainly but little worthy of consideration, there 

 is perhaps one other remaining, viz., that all or 

 many Pierides and other species of butterflies 

 possessed the same tendency to a Heliconoid 

 variation and were always everywhere striving to 

 develop this type, but succeeded only where they 

 accidentally coincided in time and place with the 

 model, the "tendency" being thus furthered by 

 natural selection. But the facts negative this 

 assumption, since such imitative variations have 



