PEDIGREE BREEDING. 



28l 



ruination of my experiments in July, and were carried over into 1905, giving 

 after transfer to Mexico in March, 1905, a Mendelian splitting into typical 

 rubrivittata and hybrid forms (text-fig. 22). These were separated and 

 reared. The pure cultures of rubrivittata showed as the result a new charac- 

 ter, namely, that its life history as well as less important characters were 

 changed, there being three generations in its yearly cycle instead of two, as in 

 the parent species, and in all the species in its immediate ancestry. 



This change in the life cycle from hibernating in every second generation, 

 as do most of the species in the genus, to hibernating in every third, is 

 striking and significant, the three generations being gone through in about 



14 Si 32 9 DECEMLINEATA Mcpherson, Kansas, July, 1003. 



I 

 II 

 III 

 IV 

 V 

 VI 

 VII 



DECEMLINEATA 

 46 $, J Vil2_ 



DECEMLINEATA 

 38,?, I 52 



DECEMLINEATA 

 91,?, 82? 



reared at Chicago. Hibernated. 

 RUBRIVITTATA - croseed with modal 9 from Chicago. 



"I 



HYBRIDS 



19,?, 1219 hibernated. 



HYBRIDS 

 35<?| 409 



In hibernation, Oct., 1905. 



RUBRIVITTATA 

 6r?,j 49 



RUBRIVITTATA 

 14?, I 189 



RUBRIVITTATA 

 48 c?, I 46 9 



In hibernation, 

 Oct., 1905. 



RUBRIVITTATA 

 11c?, I 109 



RUBRIVITTATA 

 38,?, I 30 9 



RUBRIVITTATA 

 68?, I 709 



In hibernation, Nov., 1005 



Text-figure 22. 



the same time as the two of the parent species. The cultures with rubrivittata 

 demonstrate clearly that changes in physiological characters can take place 

 rapidly, as do changes in structure, and that these changes may alter not only 

 unimportant characters, but a most fundamental one as well. We shall have 

 occasion to consider a similar case even more striking and interesting in a 

 later part of this chapter. 



With the variations albida, ininuta, dcfcctopunctata, and iimnaculothora.v 

 found in nature, I have succeeded in obtaining cultures for one or two gener- 

 ations only, and these I shall not dwell upon, since they add only slightly to 

 this account. We shall, however, meet with these in the experimental pro- 

 duction of extreme variations, where it has been possible to get cultures, 

 owing to the greatly increased number available for experimentation. 



With these variations from nature and the cultures made from them, it is 

 conclusively demonstrated that there do appear in nature rapidly developing 

 extreme variations which stand apart from the normal fluctuating variations 



