678 LECTURE XXIII. 



Further, it is not possible to frame a satisfactory explanation 

 of the fact of Adaptation without assuming the direct in- 

 fluence of the conditions of life, for Weismann's explanation 

 of this fact cannot be regarded as satisfactory (p. 66 1). He 

 endeavours to account for adaptation by attributing it to re- 

 combination, in an infinite variety of ways, of the characters 

 acquired under the influence of changes in the conditions 

 of life by the unicellular asexual progenitors of the race. 

 But it is hardly possible to conceive how that by any com- 

 bination of ancestral characters an individual could be pro- 

 duced which should be adapted to prevailing conditions of 

 life. How is it conceivable, for instance, that the adaptations 

 in the forms of their flowers, or in the structure of their 

 fruits and seeds, which are exhibited by Phanerogams, are 

 due to combinations of characters acquired by their uni- 

 cellular asexual ancestors ? 



A second objection to Darwin's view may be stated in 

 his own words : " instances could be given of similar varieties 

 being produced from the same species under conditions of 

 life as different as can well be conceived ; and, on the 

 other hand, of dissimilar varieties being produced under 

 apparently the same external conditions." With regard to 

 this, it must be pointed out that it is by no means easy 

 for the observer to assure himself of the nature and 

 extent of the difference between any two sets of external con- 

 ditions, and of the nature and extent of the modification which 

 the organism under observation may have undergone. The 

 conditions may be, to the observer, apparently very different 

 in the two cases, and yet in the points which most affect the 

 plant they may be identical ; and the converse applies to 

 conditions which are apparently similar. In illustration of 

 the possible failure in observing the modifications in the 

 organism, the following passage from Darwin may be quoted. 

 " When man can perceive no change in plants or animals 

 which have been exposed to a new climate or to different 

 treatment, insects can sometimes perceive a marked change. 

 A Cactus has been imported into India from Canton, Manilla, 

 Mauritius, and from the hot-houses at Kew, and there is 



