242 DARWINIANA. 



not been exposed to tlie contagion, and of wliicli a con- 

 siderable proportion, under the common law of ata- 

 vism, comes to be very much in the condition of a 

 people invaded for the first time by the disease. To 

 these, as we might expect, vaccination would prove a 

 less safeguard than to their progenitors three or four 

 generations before. 



Mr. Bentham is a veteran systematic botanist of 

 the highest rank and widest knowledge. He had not, 

 BO far as we know, touched upon questions of origina- 

 tion in the ante-Darwinian era. The dozen of presi- 

 dential addresses delivered at anniversary meetings of 

 the Linnean Society, from his assumption of the chair 

 in the year 1862 down to the current year — each de- 

 voted to some topic of interest — and his recent " Me- 

 moir on Composit^e," summing up the general results 

 of a revision of an order to which a full tenth of all 

 higher plants belong, furnish apt examples both of 

 cautious criticism, conditional assent (as becomes the 

 inaugurator of the quantification of the predicate), and 

 of fruitful application of the new views to various 

 problems concerning the classification and geographi- 

 cal distribution of plants. In his hands the hypothe- 

 sis is turned at once to practical use as an instrument 

 of investigation, as a means of interrogating J^ature. 

 In the result, no doubt seems to be left upon the au- 

 thor's mind that the existing species of plants are the 

 result of the diiferentiation of previous species, or at 

 least that the derivative hypothesis is to be adopted as 

 that which ofliers the most natural, if not the only, 

 explanation of the problems concerned. Similar con- 

 clusions reached in this country, from a study of the 



