Modification of Germinal Constitution of Organisms 187 



these all closely approximated the undecimlineata form 

 The census obtained late in November was: 



Signaticollis Type Mid-Type Undecimlineata Type 



o ii 1,132 



In 1906, 1907, and 1908 these cultures were allowed to 

 shift for themselves, and the food plants were nearly 

 swamped by the immigration into the glade of plants from 

 the surrounding rain forest; in fact, the whole culture was 

 allowed to engage in a most desperate struggle for its 

 existence. As far as the beetles were concerned, this was 

 simply a struggle for food. In 1908-9 the inroads which 

 had been made by other plants had so reduced the number 

 of Solanums that the food supply was inadequate. During 

 these years, however, no trace of the signaticollis type had 

 ever appeared. In 1908, material of the undecimlineata 

 type was taken from this culture to Chicago, and there 

 subjected to the tests of pedigree analysis, but without 

 any trace of the signaticollis form appearing. In both 

 experiments, however, at Praesidio and at Cuernavaca, 

 the resulting materials were different in gametic make- 

 up from the original species. Superficially, these stocks 

 could not be told from the natural species, but when used 

 as the basis of experiment under control conditions, it was 

 found that there 'resulted a difference in the behavior of 

 the subsequent hybrid generations, clearly indicating a 

 change in the gametic constitution of these groups of 

 individuals. 



A series of experiments, more conclusive and under 

 better conditions, has been carried on, using three species: 

 L. decemlineata, L. oblongata, and L. multitaeniata. Of 

 these, in nature, L. decemlineata is limited solely to the 



