MODi:^ICATlON OF COI,OR. 201 



when the temperature did not vary below the normal much beyond 5*^ to 7° 

 C, the resulting color modifications were controlled by the relative humidity. 

 Thus, in j melanic conditions were produced, but in k and / the high humidity 

 inhibited coloration slightly, so that the curve dropped back toward the nor- 

 mal. This same condition, less pronounced, was also found in m, n, and 0. 

 In experiments p to u, on account of the greatly reduced temperature used, 

 the modifications were all toward albinism. 



From these experiments the following conclusions may be drawn : 



( 1 ) When the temperature deviates above and the humidity below the nor- 

 mal the general trend of color modification is albinic. 



(2) When the temperature varies below and the humidity above the nor- 

 mal the general trend of color modification is melanic, unless the temperature 

 deviation is extreme, 15° to 25° C. below the normal, when the color trend is 

 albinic. 



(3) From ( I ) and (2) we may draw the more general conclusion that when 

 temperature and moisture are the variables in a given environmental com- 

 plex, the trend of general color modification is controlled by moisture (rela- 

 tive humidity), excepting in conditions where the temperature deviation is so 

 excessive that the ordinary physiological and developmental processes are 

 greatly inhibited (experiments p to u). In experiments approximating nat- 

 ural environmental complexes, however, moisture is the dominant factor in 

 influencing coloration. 



Experiments in which ly. dkcemi^ineata was Reared During Successive Gen- 

 erations WITH Both Temperature and Moisture Varying Together, or in 

 Opposite Directions Above or Below the Normai,. 



The object in these experiments was to rear the beetles in successive gen- 

 erations under conditions applied during ontogeny, and especially during the 

 development of the coloration. The plan was to allow each generation to 

 breed and begin its development under conditions simulating those in nature, 

 and then to let the ontogeny be completed under an environmental complex 

 deviating from the normal. By this process, repeated generation after gen- 

 eration, data was obtained as to the inheritance of somatic modifications. Of 

 the many experiments of this kind which were tried, one alone is sufficient to 

 illustrate the results obtained. 



Experiment 27. — To determine whether coloration changes produced as the result of 

 changed environmental conditions are inherited, increased, or dropped in successive 

 generations. 



Conditions. — Temperature on the average 6° C. and relative humidity 10 

 per cent above that in nature, with other conditions normal. These condi- 

 tions were planned to produce melanic tendencies in variation. 



Apparatus. — The same as in experiment 23. 



