MabCh 24, 1916] 



SCIENCE 



407 



proviaee of thought ; they tend to a return 

 to the mean of wisdom and sanity. To 

 change our simile for a moment, the ex- 

 tremist carries the ball far to the left or 

 right in an end run; but he advances it 

 somewhat, and the conservative mass of his 

 colleagues brings the ball back to the cen- 

 ter of the field and more directly in front 

 of the goal. 



It is almost hopeless to-day to look for a 

 Weismannian in the extreme sense, but 

 there is a practical acceptance of the idea 

 of the continuity and stability of the germ- 

 plasm. Probably no one now would give 

 adherence to Cope's complete program, but 

 many believe that, somehow, acquired char- 

 acters play a real part in the advance of 

 species. In my opinion, too, there are very 

 few indeed who would frankly subscribe to 

 the extreme of Bateson's doctrine regard- 

 ing the unpacking process, but there are 

 very many who admit that the Mendelian 

 law is a very important thing in heredity, 

 whether it really advances evolution or not. 



3. We should be exceedingly hesitant in 

 unreservedly condemning the leaders of 

 the past, or the theories they advanced. 

 Each one of them has done good service 

 and each has been the vehicle of some im- 

 portant truth. Perhaps none of the theo- 

 ries advanced by Darwin has been so merci- 

 lessly ridiculed as that of pangenesis. Yet 

 I find in one of the most recent utterances 

 of T. H. Morgan the following : 



There is extensive evidence from cytology, ex- 

 perimental embryology and regeneration to show 

 that all the different cells of the body receive the 

 same hereditary factors.^ 



The swing of the pendulum back from 

 the extreme position taken by Bateson has 

 surely commenced, as the following quota- 

 tions will show. 



3 "Mechanism of Mendelian Heredity," 1915, 

 p. 42. 



Castle, one of the leading American au- 

 thors in Mendelianism, says: 



The more carefully we scrutinize the mutation 

 theory the more serious do our doubts become, 

 whether it is a secure foundation to build on, and 

 again whether sport variation has had any part in 

 the evolution of species is accordingly very doubt- 

 ful.* 



The veteran zoologist, Wm. H. Dall, 

 says, in commenting on Bateson's address: 



We may admit the value of the Mendelian dis- 

 covery in its relation to low and relatively simple 

 organisms, like plants, and also that in higher or- 

 ganisms Mendelian effects can sometimes be 

 traced, but that unbridled hypothesis should be 

 permitted to cover our colossal ignorance is not 

 what we expect from such a source. When the 

 observed facts flatly contradict a hypothesis a 

 truly scientific expositor says "I can not account 

 for it," and does not cover up (to the lay mind) 

 his ignorance by the phrase of "an inhibitory 

 factor. ' ' 5 



No more honored name is at present on 

 the roster of American biologists than that 

 of E. B. Wilson, and the following quota- 

 tion from him has a weight that all must 

 recognize : 



And yet, as far as the principle is concerned, I 

 am bound to make confession of my doubts whether 

 any existing discussion of the problem affords 

 more food for reflection, even to-day, than that 

 contained in the sixth and seventh chapters of the 

 ' ' Origin of Species ' ' and elsewhere in the works 

 of Darwin. 



The next swing of the pendulum lies in 

 the immediate future, and we know not 

 what it will bring forth; but we do know 

 that it will be the means of a new advance 

 along the road to a better understanding 

 of nature's methods. 



In the meantime, what should be the 

 attitude of the systematist 1 Bateson would 

 say that he is out of the game altogether, 

 as the following quotation will show : 



* Science, Vol. XLI., p. 98. 

 5, Science, 1914, p. 245. 



