IBOOK REVIEWS. 



161 



depart indefinitely from the Original Type," by Wallace. It is interest- 

 ing to note that while Darwin collected his data chiefly from " Animals 

 and Plants under Domestication," Wallace says: — "We see, then, 

 that no inferences as to varieties in a state of nature can be deduced 

 from the observation of those occurring among domestic animals." 



Speaking of Dr. F. Darwin's belief in " the transmission of 

 acquired characters as being implied by the persistence for unnum- 

 bered generations of the successive developmental stages through which 

 the individual advances towards maturity," the author observes that 

 " Weismann's hypothesis of the continuity of the germ-plasm 

 supplies a sufficient mechanism." Assumi7ig that germ-plasm exists, 

 the ' ' persistence ' ' may be accounted for ; but is it not best to look 

 for facts ? These are perhaps more easily seen in plants than animals ; 

 and if it be true in the former, it is a strong inference that it is 

 also in animals. The ' Virginian Creeper ' never makes adhesive 

 pads before contact with a wall. A mechanical irritation i& suffi- 

 cient to invite the response. In the Japanese species the pads are 

 partially formed before contact — i.e. they are not only " acquired " 

 but " hereditary." Prof. Poulton observes: — " It is well known that 

 plants have the power of adjusting themselves to their individual 

 environment . . . the hereditary transmission of the results of its exer- 

 cise is especially dangerous." Why so? If a plant has for generations 

 adapted itself to a particular environment but cannot readapt itself 

 to another, it will die; but this is 7iot the usual result. The water 

 crowfoot is adapted to live submerged ; but it produces stronger plants 

 if the seed be sown on land. Yet it retains the " acquired " dissected 

 fohage. This example seems to refute Prof. Poulton 's assertion — If a 

 species possessing the power of individual adaptation ultimately came 

 to live permanently in one set of conditions [e.g. as a submerged 

 plant] , and thus ceased to need it, the pov/er itself, no longer sustained 

 by selection [i.e., assumed to be so], would sooner or later be lost. 

 [This is an unproven assumption.] The fleshy character of the 

 samphire is regarded as an " acquired " character, because it is proved 

 experimentally to be due to salt. Yet when grown inland it becomes 

 a thin-leaved plant. As Dr. F. Darwin says, corroborating his father,''' 

 " the permanent condition is a final result of the hereditary trans- 

 mission [of fluctuating or individual differences] by the same response 

 through a large number of generations." 



Prof. Poulton refers to the neglect of adaptation as due to Huxley, 

 who was " not a naturalist, far less a student of living nature." But 

 adaptations in plant life have been almost exhaustively studied since 

 Darwin led the way. He was the first and greatest of our ecologists. 



Prof. Poulton elsewhere says : — " This Lamarckian conclusion, that 

 the adaptive response has been caused and not merely evoked by 

 environmental stimuh is well criticized by de Vries." We do not see 

 the difference between " caused " and " evoked." The " stimulus " 



* A71. and PI. under Dom. ii. 271. 



VOL. XXXVI. 



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