174 Heredity and Eugenics 



and there gave rise to several new types during the years 

 of DeVries' observation. Some of these arose in the 

 experiments but once, as for example, 0. gigas (Fig. 63), 

 a tall, robust form with large flower, the finest of all the new 

 types. It appeared in 1895 and was one out of about 14,000 

 plants, but was not the only new type to appear in the crop 

 of that year. Six others were found: O. albida, of which 

 there were fifteen examples (Fig. 64); O. ohlonga (Fig. 65), 

 of which 176 specimens appeared; 0. rubrinervis, eight 

 specimens; O. scintillans (Fig. 66), one specimen. This 

 year gave the greatest number of new forms of any, although 

 other years (1896, 1897) gave all but the 0. gigas. 



A good idea of the real differences existing between 

 these derivative forms and the parent plants is given in 

 Fig. 67, where the plants are shown growing side by side. 



In Fig. 68 is given in condensed form the line of descent 

 and the appearance of the derivative forms from year to 

 year. 



If all be granted that is claimed for the separateness of 

 these types, and admitting also that they are absolutely 

 constant in type and in heredity, there still remains one 

 striking difference between these DeVriesian "mutations" 

 and the "sports," "saltations," etc., of other writers: 

 namely, the mutations occurred in numbers in every genera- 

 tion for a considerable period, through several consecu- 

 tive generations; the sports of Darwin appear but once, 

 rarely, and not successively. Upon the curious findings 

 in 0. Lamarckiana, DeVries has built the hypothesis of 

 a premutation period in which the germ plasm was 

 elaborating new pangenes which, when the pangenes reached 

 a certain point, broke out into visible manifestation as 

 mutants, and he further supposed that after a time the new 



