418 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



to prove the very fact of a great variability of the species, even 

 in their typical specific characters — this being denied then by a great 

 number of zoologists and botanists. And later on a mass of experi- 

 ments had to be made in order to prove that if plants and animals be 

 placed in such conditions of temperature, moisture, light, and so on, 

 as are offered in different regions of the earth, they will display ex- 

 actly those variations which are characteristic of the floras and faunas 

 of these regions, without any interference of natural or artificial selec- 

 tion. Besides, it was important to prove, and it was proved, that 

 these variations, representing in most cases adaptations to the new 

 conditions of life, could be produced by the new conditions them- 

 selves, which stimulate certain physiological functions (nutrition, 

 evaporation, the elaboration of fats, and so on), and through them 

 modify different organs. 1 



Only after this immense work had been done — and it took more 

 than 40 years — did biologists begin to investigate how far such varia- 

 tion is capable of giving origin to new races, and how many genera- 

 tions must be submitted to the modifying influences in order to pro- 

 duce a more or less stable variety. 2 



It must also be noted that at the outset inheritance experiments 

 were chiefly made with variations in the colors and the markings of 

 insects, and only now are they beginning to be directed toward the 

 far more important study of variations in physiological functions, 

 which are (as was indicated long since by G. Lewes and Dohrn,- and 

 lately by Plate) the chief agencies in the evolution of new races. 



These are the causes which explain why the inheritance of en- 

 A'ironment-variations has not yet been proved by more experiments. 

 However, it must not be forgotten that we know already two im- 

 portant groups of variations, both due to environment, which are 

 inherited, and the inheritance of which is not contested. One of them 

 is the inheritance of variations by means of bud-reproduction, and 

 the other includes the so-called " sports," described by de Vries as 

 " mutations." 



1 All this has been proved by experiment, and this is why a good-sized book would be 

 required to record the results obtained lately by Experimental Morphology. Cf. T. H. 

 Morgan's Experimental Morphology, New York, 1907 ; Przibram's Experimental-Zoologie, 

 Vienna, 1910 ; Yves Delage and M. Goldsmith, Les theories de Involution, Paris, 1909 ; 

 and so on. 



2 That time was an important element in the problem was emphatically asserted by 

 both Lamarck and Darwin, and even by Bacon. But there are Weismannians who over- 

 look it. Thus Lamarck was reproached with having enunciated two contradictory state- 

 ments in his first and second law. But such a reproach could only be made by overlook- 

 ing the time that is required to produce the changes. To use Lamarck's own words, time 

 is needed " both in gradually fortifying, developing, and increasing an organ which is 

 active, and in undoing that effect by imperceptibly weakening and deteriorating it, and 

 diminishing its faculties, if the organ performs no work" (first law). All that the 

 second law says is, that what has been acquired or lost in this way is transmitted to the 

 new individuals born from the former ; but it says not a word about the length of time 

 that the new character is going to be maintained, if the new-born individuals are placed 

 again in new conditions or returned to the old ones. These individuals evidently fall in 

 such case under the action of the slow changes mentioned in the first law. 



