88 GENETIC VARIATIONS 



different kind, so that the predetermination is such only in the 

 sense that the germ plasm is of a type that can produce these 

 structures if the conditions are favorable to them. 



6. Such new structures as a rule take origin after there has 

 been a change of environment, or a change of habit on the 

 part of the organisms, of such a sort that the nev^ structures 

 in time are useful and "meet the situation" under the new 

 conditions. 



From these and similar data, Osborn draws a number of 

 important conclusions: 



A. The new structures arise in response to a functional 

 need, in consequence of a changed environment or a change 

 of habit. 



B. But they are not induced during the life of the individ- 

 ual, like the acquired immunity of an animal. They are not 

 direct adaptations of the individual animal to conditions, with 

 inheritance of these adaptations; not "inheritance of acquired 

 characters." Rather they are, as Osborn expresses it, "secular" 

 adaptations, requiring ages for their full production. 



C. They are not "chance variations," or undirected varia- 

 tions, it is held, because they follow a definite course, toward 

 the fulfilment of a particular need. They are from the start 

 adaptive or "in the direction of future adaptations." 



Attempts have been made, on the basis of the modern study 

 of mutations, to explain these phenomena in the following 

 way. The origin and farther advance of the new structures 

 are held to be in fact the result of undirected mutations; 

 mutations occurring with many diverse effects, as in Droso- 

 phila. The individuals in which these mutations are harmful, 

 or are not beneficial, in time die out or cease to propagate. 

 They therefore do not appear in the line of descent from the 

 early to the late stages of the given structure. But in some 

 cases the mutations happen to be useful. These continue to 



