FACULTIES OF THE MINI). 255 



tected state during all the stages of his existence. Others, 

 (as the Sabell<)} construct a covering of particles of sand 

 cemented together, increasing the diameter of the tube with 

 the corresponding increase of the size of the body. Those 

 animals which construct a permanent covering with which 

 they are connected, in every period of life, are all inhabi- 

 tants of the water. Man is the only animal endowed with 

 this instinct, that inhabits the land. Parental tenderness 

 supplies his wants in the first instance, and afterwards he 

 is guided by this active powej, regulated by habit, and the 

 principle of imitation. 



As subordinate to this desire, we may here take notice 

 of the Habitations of Animals, into which they retire at 

 particular intervals. 



The most common display of this instinctive power in the 

 formation of a dwelling, may be observed in those animals 

 which burrow in the earth. These form their holes with 

 their jaws, as many insects, or with their feet, as quadru- 

 peds and some birds. The retreat sometimes consists of a 

 single apartment, while others excavate several chambers, 

 leaving the walls without a covering, or giving them a coat 

 of plaster to prevent them from crumbling down. In many 

 cases, there is only one entry, while others make use of two 

 or more. In the arrangement of the entry, this instinct 

 displays its extraordinary powers. Sometimes the en- 

 trance, as in the case of the otter and pole-cat, opens into 

 a thicket, or under the cover of a hanging bank. In 

 other cases, as that of a spider, termed by LATREILLE 

 Mygale ctEmentaria, the entrance is closed by a door 

 formed of particles of earth cemented by silken fibres, and 

 closely resembling the surrounding ground. This door, or 

 rather valve, is united by a silken hinge to the entrance, at 

 its upper side, and so balanced, that when pushed up, it 

 shuts again with its own weight. 



