THE 



AMERICAN NATURALIST 



SOME FUNDAMENTAL MORPHOLOGICAL 

 OBJECTIONS TO THE MUTATION 

 THEORY OF DE VRIES 



PROFESSOR EDWARD C. JEFFREY 



The hypothesis of the saltatory origin of species has 

 received a new impetus from the investigations of De 

 Vries,* published in his "Mutationstheorie" and subse- 



i To an address delivered in Brussels before the outbreak of the war and 

 published in Science (Vol. 40, No. 1020, July 17th.), Professor de Vries 



published in Science (Vol 39, No. 1005, April 3d.). The gist of his objection 

 to the writer's position, that (Enothera and other members of the Onagraceae 



sterility or partial sterility of their pollen, is the contention that pollen 

 sterility and gametic sterility in general is not sufficient evidence of hybrid 



place prominent geneticists for many years have recognized pollen sterility 



now become very extensive, on the Angiosperms as a whole, show very inter- 

 esting conditions in many natural families. While the monotypic species 

 and those which are isolated geographically or phenologically (that is by a 

 time of flowering later or earlier than that of the mass of species belonging 

 to the genus) have invariably good pollen, those species, which overlap in 

 their geographical range and in their times of flowering in many cases are 

 characterized by abortion of the reproductive cells. In other words pollen 



to the Rosacea?. Taking a further illustration from the large family 

 Ranunculacete, Ranunculus acris and li. repens, which overlap both in range 

 and time of flowering have pollen, which is often largely imperfect, particu- 

 larly in the first mentioned species. S. rhomboideus on the other hand, 

 flowering in the very early spring has perfect pollen development. 



