258 GENERAL BIOLOGY 



the reverse is the case. It has been amply demon- 

 strated that there is nothing specific in the effect 

 of these variations in the environmental complex. 

 Extreme heat and extreme cold will most often pro- 

 duce identical effects. Tower, in the course of long 

 experimentation with the potato beetle, has shown 

 that the exposure of the developing insect to moist 

 conditions produces a dark (melanic) beetle, whereas 

 the relative absence of moisture produces a cor- 

 responding lack of pigment (albinism). It is inter- 

 esting to discover that the beetles found in nature 

 in dry countries such as the southwestern United 

 States are albinic, whereas those found in clayey soils 

 in northwestern United States are melanic. The 

 same conditions evidently have produced the sunn- 

 result, both in the laboratory and in a state of nature. 



Influence of Food. It is well known that many 

 flowers may be artificially colored by allowing them 

 to soak up various dyes. The presence or absence of 

 numerous other chemical substances in the soil ;il>o 

 produces a difference in habit of growth, size, color, 

 etc. A considerable amount of lime, e.g., will induce 

 a hairiness on leaves and stems together with a more 

 abundant foliage. It has been observed, too, that 

 caterpillars fed on a different food plant from that 

 to which they are accustomed sometimes develop 

 into moths and butterflies with quite different color 

 markings from the normal, although there is no 

 relation between the color markings and the specific 

 food plant. The color of the caterpillar in many 



