DWELLINGS 1609 



life there, habitually staying in the earth and pursued 

 by numerous enemies, especially half-wild dogs. It 

 tries to hold its own, but its wings and beak do not 

 suffice to protect it, and the race would have com- 

 pletely disappeared if these birds were not able to 

 resist, owing to the prudence with which they stay 

 within their dwellings. They profit by a natural 

 retreat, or one constructed in rocks or beneath roots 

 of trees ; they only come out when impelled by hun- 

 ger, and return as soon as they can in case of danger. 



A large number of animals also hollow out shelters 

 for their eggs, with the double object of maintaining 

 them at a constant temperature and of concealing 

 them. Most reptiles act in this manner. 



It is not only land animals which adopt this custom 

 of living in the earth, and there sheltering their off- 

 spring. Fish also make retreats on the bank or at 

 the bottom. To mention only one case, the bullhead 

 (Cottus gobio) of English rivers, which spawns in the 

 Seine in May, June, and July, acts in this manner. 

 Beneath a rock in the sand it prepares a cavity; then 

 seeks females and brings them to lay eggs in its little 

 lodging. .During the four or five weeks before they 

 come out it watches the eggs, keeping away as far as 

 possible every danger which threatens them. It only 

 leaves its position when pressed by hunger, and as 

 soon as the hunt is concluded, returns to the post of 

 duty. 



Other animals when digging have a double object: 

 they wish to shelter themselves, and at the same time 

 to find the water which they need for themselves or 

 for the development of their young. 



