Modification of Germinal Constitution oj Organisms 191 



sixth hybrid generation was found emerging. These were 

 taken to Cliicago and subjected to analytical experiments and 

 were found to breed true, both in group and in pedigreed cul- 

 tures, with this exception, that in both the pedigreed cultures 

 there occurred from time to time sporadic variants often 

 standing a considerable distance apart from the rest of the 

 population, which, when inbred, either with sports like 

 themselves, or back to the parent type, gave behaviors which 

 in ever}' way are comparable to the behavior observed in 

 many of the forms which are supposed to have arisen by a 

 mutative process. These strains were kept through the 

 years 1908 and 1909, and gave results which strongly 

 suggest that the interpretation of a mutative period as 

 described b>' DeVries in O. Lamarckiana, may well be the 

 variabilit}' which follows complex processes of hybridization. 



In 1906 operations were begun at Orizaba, and in May 

 the same three species from the same original stocks were 

 mated. Conditions at Orizaba are decidedly different from 

 those in the Balsas Valley. The city is 2,000 ft. higher in 

 altitude and the climate is very different. In the Balsas 

 VaUey during the summer the days are bright and hot, 

 with even showers. At Orizaba, in the location chosen 

 at the foot of the Sierra Escamela, it is never above 90° 

 even on the hottest days, and the nights are always cool, 

 owing to the downward draught of cool air from the moun- 

 tains which flows over the valley at night. The relative 

 humidity is high at all times, and the precipitation during 

 the season was 74 inches. 



Under these conditions the crosses which were made 

 thrived as far as certain members were concerned: the 

 L. miiUitacniata individuals were decidedly reduced by the 

 conditions under which they were hving and the L. oblongata 

 individuals were hampered considerably, but to a lesser 



