Inheritance of Habitat Effects. 57 



increase in average length of one or two cm., the roots change 

 as much but the reproductive branches and floral organs retain 

 their alpine characters. The silght modifications undergone by 

 these features were seen to reach a maximum and to decrease in 

 the latest generations cultivated. The structural changes and 

 implied functional accommodations are indubitably direct 

 somatic responses, and it is suggested that their annual repetition 

 through the centuries may have resulted in their fixation or 

 permanency. 



A related phase of the subject is that of the interposition 

 of environic factors in mutation and hybridization. DeVries 

 has repeatedly called attention to the fact that the composition 

 of hybrid progenies of mutants with each other and with the 

 parental form might be altered by nutritive conditions, and the 

 author has cited the fact that mutations were made by Oenothera 

 Lamarckiana in the climate of New York, which had never been 

 seen in Amsterdam. Furthermore, in discussing the divergent 

 results of DeVries and myself, obtained by crossing the same 

 forms in Amsterdam and New York, the suggestion was made 

 that "the manner in which the various quahties in the two 

 parents are grouped in the progeny might be capable •£ a wide 

 range of variation. Many indications lead to the suggestion that 

 the dominancy and prevalency, latency and recessivity of any 

 character may be more or less influenced by the conditions 

 attendant upon the hybridization; the operative factors might 

 include individual qualities as well as external conditions." 

 Much more striking evidence upon the matter has been recently 

 obtained by Tower in intercrossing species of the potato beetles 

 in their habitats in southern Mexico, and at the Desert 

 Laboratory. 



Zoologists have carried out numerous tests on the eff"ects of 

 climate on beetles, butterflies, lizards, crustaceans and mammals 

 with results that vary in detail but confirm the general conclu- 

 sions to be drawn from plants. From a study of all of the evi- 

 dence we are warranted in saying that the characters resulting 

 from the action of external conditions, are inherited in many 

 instances. Such heritable qualities may appear at once under 

 the influence of the exciting agency, and thus constitute a mu- 

 tational change, or the alteration may begradual and cumulative. 

 In seme cases ancestral characters may be caused to reappear, 



