354 



SCIENCE 



[N. S. Vol. XXVIII. No. 716 



er's letter) spoke in defense of the doe- 

 trine of evolution. I am sure that every 

 member of this association will be glad to 

 be reminded that Sir Joseph Hooker is, 

 happily, still working at the subject that 

 his lifelong labors have so greatly ad- 

 vanced, and of which he has long been 

 recognized as the honored chief and leader. 



You will perhaps expect me to give a 

 retrospect of the progress of evolution 

 during the fifty years that have elapsed 

 since July 1, 1858, when the doctrine of 

 the origin of species by means of natural 

 selection was made known to the world in 

 the words of Mr. Darwin and Mr. Wal- 

 lace. This would be a gigantic task, for 

 which I am quite unfitted. It seems to 

 me, moreover, that the first duty of your 

 president is to speak on matters to which 

 his own researches have contributed. My 

 work— such as it is— deals with the move- 

 ments of plants, and it is with this subject 

 that I shall begin. I want to give you a 

 general idea of how the changes going on 

 in the environment act as stimuli and com- 

 pel plants to execute certain movements. 

 Then I shall show that what is true of 

 those temporary changes of shape we de- 

 scribe as movements is also true of the 

 permanent alterations known as morpho- 

 logical. 



I shall insist that, if the study of move- 

 ment includes the problem of stimulus and 

 reaction, morphological change must be 

 investigated from the same point of view. 

 In fact, that these two departments of in- 

 quiry must be classed together, and this, 

 as we shall see, has some important results 

 — namely, that the dim beginnings of habit 

 or unconscious memory that we find in the 

 movements of plants and animals must 

 find a place in morphology; and inasmuch 

 as a striking instance of correlated mor- 

 phological changes is to be found in the 

 development of the adult from the ovum, 

 I shall take this ontogenetic series and at- 



tempt to show you that here also some- 

 thing equivalent to memory or habit 

 reigns. 



Many attempts have been made to con- 

 nect in this way the phenomena of mem- 

 ory and inheritance, and I shall ask you 

 to listen to one more such attempt, even 

 though I am forced to appear as a cham- 

 pion of what some of you consider a lost 

 cause— the doctrine of the inheritance of 

 acquired characters. 



MOVEMENT 



In his book on "The Power of Move- 

 ment in Plants" (1880)^ my father wrote 

 that " it is impossible not to be struck with 

 the resemblance between the foregoing 

 movements of plants and many of the ac- 

 tions performed unconsciously by the 

 lower animals." In the previous year 

 Sachs^ had in like manner called attention 

 to the essential resemblance between the 

 irritability of plants and animals. I give 

 these statements first because of their sim- 

 plicity and directness; but it must not be 

 forgotten that before this Pfeffer* had be- 

 gun to lay down the principles of what is 

 now known as Reizphysiologie, or the 

 physiology of stimulus, for which he and 

 his pupils have done so much. 



The words of Darwin which I have 

 quoted afford an example of the way in 

 which science returns to the obvious. 

 Here we find revived, in a rational form, 

 the point of view of the child or of the 

 writer of fairy stories. We do not go so 

 far as the child; we know that flowers do 

 not talk or walk; but the fact that plants 

 must be classed with animals as regards 

 their manner of reaction to stimuli has 

 now become almost a commonplace of 

 physiology. And inasmuch as we our-- 

 selves are animals, this conception gives us 



= P. 571. 



'Arleiten, II., 1879, p. 282. 



' " Osmotisehe Untersuchimgen," 1877, p. 202. 



