606 / 'aliclify of the Pocfrinc of Mutation. 



BoRRADAiLLE^ Working with decapods, came to the con- 

 chision that great difficulty stands in the way of the ex- 

 ])lanati<)n of si)ecitic (hffercntiation \)\ means of or(hnar\' 

 natural selection.^ ]Mr. R. Lauterborx was so kind as 

 to draw my attention to the appearance of the yellow 

 Atrofya Belladonna lufca, and to the evidence given on 

 this variety hy Dr. SciiiJz.- Dr. Raatz was also kind 

 enough to send me some seeds of a most remarkahle 

 shiny hrown variety of the sugar-heet which suddenly 

 arose in the cultures of Klein-A\'anzlehen, and from which 

 I obtained fine instances of the new character in my 

 garden. 



I have only given a selection from the long list at 

 my disposal. i\Iy object vras simply to show that the 

 doctrine of mutation already finds adherents everywhere 

 and is supported by a l)r(^ad foundation of facts. This 

 justifies the expectation that the difficulties which still 

 stand in its way will ultimately be overcome. 



§ 7- THE EXPLANATION OE ADAPTATIONS. 



Ever since the belief in tlic common origin of organ- 

 isms has been recoe'nized as a basis for investigation and 

 speculation, one as])ect of the problem has aroused the 

 special interest both of the author and of the student, viz., 

 the explanation of adaptations. As a matter of fact this 

 problem lies outside the scope of the present book, which 

 is only concerned with tlie empirical foundations of the 

 theory of descent. Nevertheless it seems to me that it 



M.. A. P)ORRADATLLE, Marine Crustaceans. The Fauna and Gc- 

 ograpliy of tlic Mnldivc and Laccadivc Archipelagoes. Vol. T. Pt. 2. 

 page 197. 



' Anifl. BcriclU i'lhcr die 33. J^ersaninil. d. Nattirf. iind Acrzte, 

 Bonn. Sept., 1854 ( r>onn, 1859), p. 139. A single specimen of the 

 plant had been found a few j^ears previously in the Black Forest. 



