248 WILLIAM LAWRENCE TOWER. 



recorded in a previous publication, along with the probable 

 relations and phyletic history and relations of these organisms. 



Both of the southern species in all of the locations in which 

 I have information concerning them, must encounter during 

 their period of hibernation desiccation in differing degrees of 

 intensity, from a rather low one on the Plateau of Ahnuac, to 

 intense conditions in the deserts of San Luis Potosi, and in 

 hibernation do not go deep in the soils, but remain in the upper 

 layers, or near the surface, whereas decem-lineata in its range 

 goes deep in the soil. Owing to the disturbed and impossible 

 conditions in Mexico, since this condition was discovered in the 

 Tucson cultures, it has been impossible to either obtain new 

 materials from the Mexican locations, or make desirable observa- 

 tions and tests that might have been made had more happy 

 conditions prevailed. Fortunately some experiments made in 

 1908 and 1909 for other purposes have given data as a by-product 

 that is of interest in this connection. 



In both of these years crosses were made in the garden at 

 Chicago of the C 100 stock and freshly obtained materials of 

 both L. oblongata and L. midtitceniata, the latter from Chapultepec 

 near the City of Mexico, the former from Cuernavaca in the 

 State of Morelos, Mexico. These were of the first summer 

 generation in all species, and the FI populations were hibernated 

 in the garden at Chicago under the full intensity of the winters 

 of 1908-9 and 1909-10, with the results that are shown in Table 

 X., all the materials being from the mating of pairs, and not 

 from population cultures. 



The experiences in the crossing of the three species shown in 

 Table X. with the elimination of the hibernation FI population 

 during the winter months is highly suggestive, and would give 

 the basis for an interesting series of tests were it possible to 

 obtain fresh materials from the Mexican locations. The com- 

 plete dominance of the Mexican species over decem-lineata in 

 the matter of survival in hibernation, indicates that in them the 

 same or essentially the same condition exists as in the cultures 

 at Tucson. Unfortunately, I have not had the necessary mate- 

 rials for the testing of their resistance to desiccation, and can 

 therefore only conclude that the close identity in the survivals 



