Varietäten, Descendenz, Hybriden. 197 



redrayed varieties developed under cultivation, or very rarely 

 found wild as Single sports, the distribution of the red is controlled 

 by „markingfactors", which existed prior to and indepently of the 

 color-development through which they are made manifest. The 

 independent existence of these marking factors is shown not only 

 by their behavior in heredity, but also by their partial or faint 

 appearance in the orange (wild) forms, and their revelation through 

 photography. 



These marking-faktors form a quite definite System in the 

 red-coloured garden sunflower- varieties, obtained by the writer 

 through Crossing an original wild red sport {Helianthus annuus 

 lenticularis var. corotiatus) with garden varieties. Their indepen- 

 dence of the shade of color is shown by the fact that the chestnut- 

 red [coronatus] and wine-red {vinosus) groups afford exactly parallel 

 series of types. 



Independently of the originally wild found H. annuus coro- 

 natusj the species H. cucumerifoUus develops a red colour in some 

 of its varieties. The patterns are on the whole very different from 

 those of H. annuus. 



Hybrids between varieties of H. anmius and of H. cucumeri- 

 foUus have been grown by the writer. One of these, a crossing 

 of a vinous H. annuus and a very pale H. cucumerifoUus, has a 

 dark disc and rays varying from clear bright lemon to pale prim- 

 rose. When the flowers of this remarkable hybrid first open, the 

 basal third or more of the rays is suffused with the anthocyan 

 color. With time, this red colour fades out completely, leaving in 

 its place an orange suffusion. The loss of the red color with 

 maturity can be understood on the supposition that a deoxidising 

 factor or substance develops. M. J. Sirks. (Wageningen). 



, A., Progressive evolution and the origin of spe- 

 cies. (American Naturalist. IL. p. 149—182. 1915.) 



A critical discussion of the mentioned problems: the origin 

 of species is a different problem from that of the cause of progres- 

 sive evolution. 



It appears to the writer that the power of profiting by exper- 

 ience (Jennings) lies at the root of the problem of progressive 

 evolution and that in it a chief cause of progressions is to be 

 found. Jennings has spoken of the principle involved here as the 

 „Law of the readier resolution of physiological states after repeti- 

 tion" and similarly the writer thinks we must recognize a „Law 

 of the accumulation of surplus energy'' as resulting therefrom. By 

 this law each generation gets a better start than its predecessor, 

 and is able to carry on a little further its struggle for existence 

 with the environment. 



The writer endeavours first to account for the fact that pro- 

 gressive evolution actually occurs by attributing it primarily to the 

 power possessed by living protoplasm of learning by experience 

 and thus establishing habits by which it is able to respond more 

 quickly to environmental Stimuli, and next inquires what it is that 

 determines the definite lines along which progress manifests itself. 

 He does not see any reason to distinguish between somatogenic 

 and blastogenic characters. All the characters of the adult animal 

 are acquired during ontogeny as the result of the reaction of the 



