Architecture in the Animal Kingdom. 117 



much and the nest threatened to dry up, a change to 

 the opposite was effected ; the nest was constructed as 

 flat and as low as possible with very few openings on 

 the surface. The propriety of such proceedings is cer- 

 tainly striking. Often enough the same can be 

 observed also in nature, both in those species that 

 build only domes of earth, and in those that build 

 regular ant-hills. It is a fact even noticed by farmers 

 and ascertained by myself repeatedly, that in dry and 

 hot summers the hills of wood ants are lower and 

 flatter than in moist and cold summers. The first way 

 of building is- for the purpose of reducing evaporation 

 to the lowest limit and to offer to the hot rays of the 

 sun but a small surface to shine upon ; on the other 

 hand, the higher and the more vaulted the hills are, 

 the easier is the drainage in case of rains, and the 

 greater are the evaporating and heating surfaces. 

 Indeed, ants would have to be very intelligent, if their 

 own reflection should lead them to modify their nests 

 so prudently. Yet, considering that the dome shape 

 for the nest includes in principle these quasi-intelli- 

 gent adjustments to the variations of temperature and 

 moisture, which can be traced, in consequence, to the 

 specific manner of building proper to the ants in 

 question, it is clear that instinct and not intelligence 

 is the guiding principle; for, the specific plan of the 

 building is, no doubt, instinctive, as is acknowledged 

 at least by scientific authors. In adjusting, however, 

 their instincts to changing circumstances, the animals 

 are influenced by sensitive perceptions and experi- 

 ences, which are nothing else than the natural exercise 

 of the same instinctive power of cognition, on which is 



