pedigree: breeding. 285 



These experiments with miilfifcBniata and its transmutations, riihicunda 

 and melanothorax, simply confirm and extend the results obtained from cul- 

 tures of decenilineata and its descendant species, but are much clearer in 

 many respects than the culture with decemlineata. This is especially true in 

 the last culture described, where there was a clear and unmistakable Men- 

 delian splitting of the hybrids into D -\- 2DR + R, which was continued for 

 several generations. This behavior in crossing and the complete heritable 

 quality of the modifications fotmd in nibiciinda and melanothorax show con- 

 clusively that in these forms we have to deal with variations of permanency, 

 which are able to take part in the evolution of species. 



This pedigree breeding in Leptinotarsa, which has been extended to other 

 species of the genus as well as to the two described above, brings us to several 

 interesting and suggestive conclusions. 



( 1 ) It is demonstrated that among the fluctuating variations there are indi- 

 viduals which are able to transmit their particular variations and give rise 

 by selection to a race, while the majority are not able to hand on their partic- 

 ular conditions to their progeny. Races developed by selection from such 

 variations have not by the methods used been carried beyond the normal 

 limit of variability of the species, which circumstance may be attributed 

 either to the inefficiency of selection to overstep the normal limits of varia- 

 tion, or, with more probability, to imperfect methods, and to the brevity of 

 the experimicntation. At present I see no means of deciding which is the 

 correct solution of the limitation found in race formation through selection. 



(2) It is demonstrated that there are found at irregular intervals in nature 

 and in cultures extreme variations which differ from the parent species in 

 many and constant characters, and are shown to breed true to type. More- 

 over, in crossing, these formiS behave as do species, so that no matter what we 

 call them or how we attempt to explain them and their rapidity of develop- 

 ment, the facts as stated above are clearly shown. 



(3) It was found in some of the cultures where selection was aided by 

 changed environment that heritable fluctuating variations and extreme varia- 

 tions were greatly increased in number. It was further recorded that at 

 Cabin John Bridge unusual conditions in the environmental complex pro- 

 duced an unusual number of these variations. Further, in the discussion of 

 place variations I have shown that when the polygon of variation of these 

 beetles swings toward extreme conditions, it is accompanied by an increased 

 production of these peculiar and extreme variations, and that when the 

 environmental complex assumes a normal or modal condition the produc- 

 tion of these variations also becomes modal — that is, very few are produced. 

 This convergence of evidence from diverse sources m^ost strongly suggests 

 that the production of numbers of heritable, fluctuating variations, or the 



