1 90 APPENDIX 



3, 60, 49, 9, ii, and 21 times. The mutants lata, oblonga, rubrinervis, and 

 scintillans appeared frequenty. 



In the fourth generation along with 14,000 lamarckiana plants there ap- 

 peared 41 gigas, 15 albida, 176 oblonga, 8 rubrinervis, 60 nanella, 63 lata, and 

 i scintillans, all bred from lamarckiana seed. In the fifth generation, simi- 

 larly bred from pure lamarckiana seed, among 8000 lamarckiana plants were 

 found 25 albida, 135 oblonga, 20 rubrinervis, 49 nanella, 142 lata, and 6 sw- 

 tillans. In the fourth generation one plant in 80 was oblonga. In the fifth 

 generation one plant in 60 was oblonga. De Vries himself says, "A [par- 

 ticular mutation] therefore, is not born only a single time, but repeatedly, 

 in a large number of individuals and during a series of consecutive years." 



The mutant oblonga differs from the parent species, lamarckiana, not in 

 a single feature, but in an elaborate complex of characters. The other mutants 

 likewise are distinguished from lamarckiana by a complex of characters rather 

 r han by a single feature. 



The mutations can hardly be entirely fortuitous if, for several generations, 

 out of every thousand offspring of pure lamarckiana parents, there appear 

 more than ten plants marked by the particular complex group of characters 

 which designate oblonga. Were oblonga demarcated from lamarckiana by 

 but a single character it would be remarkable to find it appearing repeatedly 

 and in such numbers. When we remember that it is defined by an extensive 

 series of characters differentiating it from lamarckiana and from all other 

 mutants observed, are we not led to the conclusion that mutation in (Eno- 

 thera lamarckiana is not wholly fortuitous, but is to a degree predetermined, 

 that there is some tendency to the production of the oblonga and other types 

 in numbers much greater than would be secured by purely fortuitous and 

 indeterminate mutation ? 



It seems of much interest that the evidence from paleontology, so long 

 emphasized by Osborn and other American students, in favor of determinate 

 variation (or mutation) should be borne out by such careful observations as 

 those of De Vries in so different a field of research. 



It is possible that (Enothera lamarckiana is a hybrid and that its mutation 

 is due to its hybrid character. I know of nothing, however, to indicate that 

 this is the case. 



These observed phenomena of determinate mutation suggest an explana- 



