HEREDITY, AND THE ORIGIN OF SPECIES MACDOUGAL, 521 



In the case of the appearance of characters not hitherto borne by 

 the main stock the case is not so clear, especially as we feel fairly cer- 

 tain that the saltations do ensue, in seed mutants at least, in single 

 cells. Here the theoretical side of the case seemed least supported by 

 facts, and I set about supplying the deficiency, with what success you 

 ma}^ presently judge. 



Omitting the detail of technique, I may say that strong osmotic 

 reagents and weak solutions of stimulating mineral salts were in- 

 jected into ovaries in such manner that unfertilized ovules were 

 subjected to the action of the fluids, which killed many of them, but 

 which gave the much-desired results in a few. In Lamarckiana 

 the frequency and character of the known mutants was unaffected, 

 but in the progeny of hiennis was found a single individual consti- 

 tuting a type hitherto unknown. This single aberrant individual 

 might have been a mutant of low frequency, comparable to gig as de- 

 rived from LaTrmrckiana, and its recurrence here might have been 

 merely a matter of chance. However, in another species of evening 

 primrose, Raimannict odorata, a flower which belongs to a separate 

 genus of the family and is not known to be mutating, the treatment 

 described resulted in a large number of aberrant individuals of a 

 hitherto unknown type. Some of these, which show a shorter life 

 cycle than the parental form and many anatomical divergencies, 

 have been brought to bloom and to maturity, and the new form is 

 obviously a potential species. In this experience, exemplified by 

 specimens of the normal jjarental forms and aberrant mutants, I 

 am able to offer you conclusive proof that agencies external to the 

 cell may induce mutations, and consequently exert a profound influ- 

 ence on heredity. It would not be well to exaggerate the importance 

 of this result, yet it is evident that the establishment of this fact 

 marks a long step forward in the experimental study of inheritance 

 and the origin of species. 



While the method described is of interest as having possibilities 

 for our intervention in the evolution of organisms, it becomes much 

 more so if similar results may be exiDected in a state of nature. 



Such a parallelism is to be found in the unusual intensities of the 

 environ ic factors of light, temperature, moisture, etc., which have 

 been used by Tower in the modifications of LejJtinotarscv which he 

 has secured. Here, of course, the entire soma as well as the germ 

 plasm is subject to the action of the inciting agent. The various 

 distributional agencies by which seeds are constantly being carried 

 far beyond the limits of the customary range of their various environ- 

 mental conditions must result in the exposure of developing indi- 

 viduals and mature germ plasm to unusual intensities, which might 

 well be responsible for such results. Thus a stream takes its rise 

 near the montane plantation of the Desert Laboratory and flows 



