NEW TYPES AMONG ANIMALS 151 



the variety ichnuse which lives in Corsica and Sardinia. In 

 another experiment Standfuss subjected the nymphae, or newly 

 hatched young, of fifty species to temperatures ranging from 

 — 4°F upward. The method was to expose the nymphae to the 

 low temperature twice per day for a period of from two to four 

 hours. This was done for five or six days. Betweenwhiles the 

 nymphag were kept at a temperature of over 40°F. The change 

 from warm to cold and back again was always gradual, lasting 

 about half an hour. When the nymphae of these various species 

 developed into butterflies it was found that from 2 per cent 

 to 15 per cent were variants from the ordinary types. Some of 

 these variants were so extreme that they might be classed as 

 mutants. The degree of variability was in proportion to the 

 lowness of the temperature. No mutants were observed when the 

 temperature was reduced to 32°, even though this continued twelve 

 hours, but when it was lowered to 23° unusual forms began to 

 appear. When the same experiments were tried with high tem- 

 peratures running up to 108° and even 113°, the same variability 

 appeared. In some cases the form of the mutants was the same 

 as in the cold experiments, but generally there was a difference. 

 Some of the unusual forms are found in nature, and may be re- 

 garded as ancestral forms. This is especially true of the ones 

 due to heat. This is natural, since temperatures above 100 may 

 occur on hot banks where the eggs are exposed to the sun, while 

 extremely low temperatures are almost unknown at times when 

 the nymphae are developing. In general, both extremes of tem- 

 perature retard the development of the insects, and the slower 

 development is accompanied by other changes. When the aber- 

 rant insects were bred under normal conditions there was a very 

 slight inheritance of their abnormality, but not enough to be of 

 great significance. 



For our present purpose the importance of these butterfly 

 experiments lies in the fact that they show how brief extremes 

 of either heat or cold may alter the form of a species. It will be 



