NOTEMBEE 29, lfl07] 



SCIENCE 



745 



factors a readjustment of all the others 

 sooner or later ensues. 



There are two other laws which I per- 

 sonally regard as demonstrated, although 

 they have not yet reached the stage of 

 axiomatic truth. These are: (4) that all 

 changes in ontogeny, environment and se- 

 lection soonei* or later are reflected in he- 

 redity; (5) that all changes in heredity 

 originate (a) either from within (keeping 

 in mind always the law of the four insep- 

 arable factors) or (&) they originate from 

 without through ontogeny, environment or 

 selection. 



The origin of new characters, not the 

 origin of species, is the central problem in 

 evolution. In using the word originate I 

 do not imply cause; I use "originate" 

 simply to imply appearance in order of 

 time. 



I. HEREDITY AS IT APPEARS TO THE 

 PALEONTOLOGIST 



I may now restrict the present discussion 

 to heredity as it appears to the paleontolo- 

 gist. As compared with his brother and 

 sister zoologists the paleontologist enjoys 

 certain peculiar advantages and labors un- 

 der certain disadvantages. 



First, it is a decided advantage that the 

 paleontologist as an observer is practically 

 immortal; that is, if the two or three mil- 

 lion years in which he is able to follow 

 certain characters constitute a reasonable 

 longevity. Concentrating his attention on 

 the history of individual characters, entire- 

 ly irrespective of the species question, 

 which is wholly a by-question, the paleon- 

 tologist may trace such individual charac- 

 ters from their origin through their various 

 changes, through their entire history, in 

 fact. In this sense he is immortal. The 

 zoologist and experimentalist (e. g., de 

 Vries, Bateson, Morgan), on the other 

 hand, is mortal. First, he is not always in 

 a fair position to judge which characters 

 are important and which are unimportant. 



This, for instance, is the chief difficulty 

 with Bateson 's first great work, ' ' Materials 

 for the Study of Variation." Second, the 

 zoologist and experimentalist is too short- 

 lived to observe and measure those changes, 

 if such exist, which are so excessively slow 

 as to be invisible and immeasurable by his 

 mortal eye, and he is most naturally led to 

 the conclusion that visible, observable and 

 measurable changes, viz., saltations, discon- 

 tinuities or mutations (of de Vries) are 

 the most important if not the only changes. 

 Having pointed out the peculiar oppor- 

 tunity of the paleontologist, let us omit 

 discussion of all other modes or sources of 

 change and concentrate our attention on 

 what is certainly the most vital point, 

 namely, the origin of new characters in 

 heredity. We shall, therefore, begin by 

 considering this origin as a question not of 

 ontogeny, nor environment, nor selection, 

 but of heredity pure and simple. By this 

 statement we do not commit ourselves either 

 way upon the question of the inheritance 

 of new ontogenetic or environmental char- 

 acters, we simply confine the subject to 

 changes which first appear through hered- 

 ity, that is congenitally or at birth. 



II. THE RATE OP ORIGIN OF NEW CHARACTERS 



Thus we come to the paleontologist as a 

 stiulent of heredity. What are his peculiar 

 advantages and disadvantages in this lim- 

 ited field of observation? Our answer is a 

 bit embarrassing because we find that as to 

 the velocity or suddenness of origin of 

 characters paleontologists have not thus far 

 agreed; they have reached two opposite 

 opinions, as follows : 



First opinion : Hypothesis of sudden ap- 

 pearance. This was first set forth by 

 Geoffroy St. Hilaire, and has been advo- 

 cated by Cope, Dollo, Smith Woodward 

 and other paleontologists. 



Two unanswerable criticisms of this 

 opinion may be made. First, in attempt- 



