788 



SCIENCE. 



[N. S. Vol. IV. No. 100. 



it has not been made in the study of 

 adult characteristics. In the anatomy of 

 the different races of man, for example, it 

 is demonstrated that many features are 

 fundamental race characters, while others 

 are merely the expression of certain habits, 

 such as modes of walking, climbing, squat- 

 ting, etc. The studies of Lane upon the 

 anatomy of laboring men of different trades 

 prove that entirely new structures, such as 

 articulations and facets, may be developed. 

 This has an important bearing upon the 

 scope of the ' predisposition ' principle. N"ew 

 facets do not arise because there is a pre- 

 disposition at a certain point to form a facet, 

 but because the local tissue reactions at 

 that point under stimulus result in a facet. 



Such ontogenic variations may extend 

 over an enormously long period of time, and 

 it is very obvious that they anticipate the 

 future course of evolution, so far, at least, 

 as all parts of the body are concerned which 

 are directly modified by stimuli. Thus, 

 whether these ontogenic variations are in- 

 herited or not, they predetermine the course 

 of evolution. They set a groove, as it were, 

 along which evolution must take its course. 



These variations, further, are of so per- 

 fect a character that they have been by 

 nearly all observers misinterpreted. They 

 have been wrongly considered as repre- 

 senting phylogenic evolution, but such evo- 

 lution is a matter of constitutional or stirp 

 variation, as shown by the well-known ex- 

 amples of the pigmentation of the lower 

 side of the flounder and of the entire body 

 of the colorless Proteus when exposed to 

 light. If these animals are contrasted with 

 an albino type, such as the albino breed of 

 Amblystoma, the real difference becomes 

 apparent. 



Thus the case appears to be established 

 that ontogenic evolution parallels, and 

 in many parts of the body anticipates, 

 phylogenic evolution by enormously long 

 periods of time. "We have in these facts 



a partial explanation, at least, of determinate 

 'variation. The straight lines which certain 

 characters follow are simply guided by onto- 

 geny. In many structures the inherent adap- 

 tive power of the organism is so great that 

 it can conform sufficiently to its new envi- 

 ronment without any change in the stirp. 



Two questions remain : (1) whether such 

 evolution is accumulative ; (2) what rela- 

 tion it bears to phylogenic evolution. These 

 will be discussed at the next meeting of 

 the Section." 



This meeting was held upon May 8th. 



" Continuing the subject discussed at the 

 last two meetings, it has been questioned 

 whether this ontogenic evolution can prop- 

 erly be considered evolution at all. It ap- 

 pears, so far as all those characters are con- 

 cerned which are adaptively plastic, that 

 the first stages of their true evolution must 

 be ontogenic. Subsequently, the same 

 changes become phylogenic, but the passage 

 from one to the other is so gradual and insen- 

 sible that they must all be considered part of 

 the same process. Ontogenic evolution, then, 

 represents the extreme changes in organisms 

 possible during individual development; 

 changes in color, hair texture, plumage, 

 scales, and the greater or less ossification 

 of the skeleton; in the forms of the joints 

 and articular surfaces ; in the development 

 of the nervous centers and the muscular 

 system ; in short, every change which does 

 not involve a change of stirp. 



The chief question remains whether such 

 evolution is accumulative. It is obviously 

 accumulative if the change of environment 

 becomes more intense and so far as new habits 

 in successive generations become accumula- 

 tive by practice and imitation. In the 

 case of plants exposed through several gen- 

 erations to the same environment there is 

 observed a marked loss of stability; thus 

 the ontogenic variations are more marked 

 in each successive generation. 



But certainly the crucial point is what 



