igS FlcrcJily and Eui^cnics 



from time to time of attributes brought into the strain by 

 h}'bridization, and which reappear in every generation, or in 

 frequent generatit)ns, by some process akin to Mendelian 

 segregation. 



It seems unreasonable to advance, as has DeVries, the 

 idea of a premutation period, with a gradual development 

 of inxisible pangenes, and then a final bursting of these 

 pangenes into a full-fledged mutation period, followed by a 

 gradual d}'ing awa\' of the mutation period which leaves 

 a species in a condition in which it does not produce these 

 sports. Rather, the explanation which Bateson suggested, 

 and which I have shown to be capable of creation in these 

 SA'nthetic experiments, is far more plausible and more 

 likeh' to be the real explanation of the t\q3e oi behavior 

 found. 



This raises a very large question — one that has been 

 raised man}' times — as to whether natural species may not 

 be hybridization complexes rather than pure line cultures 

 isolated by some sort of selection, as has been presupposed 

 since the time of JJarwin. I have found that in nature, 

 crossing, especially between these chrysomelid beetles, is 

 b}' no means uncommon, and very frequently results in 

 adult progeny in nature, some of which have been described 

 as species. These natural cases of hybridization have 

 been obser\'ed in the last half-dozen years along the edge of 

 the ^Mexican plateau. Some other species of chrysomelids, 

 from the same general region, especially some species of 

 Labidonieni, have a variabihty strongly suggestive of a 

 similar origin. I have found that Lalndomcra siiturcUa 

 Che\'r., of which many sharply marked variations have 

 been described, gives a variability in pedigreed cultures 

 that is strongly suggestix'e of the species ha\-ing arisen 



