DWELLINGS 1623 



heap. The bird throws new material on the summit 

 until the whole is of suitable height. This detritus 

 ferments when left to itself, and a gentle heat is 

 developed in the centre of the edifice. The Cathe- 

 turus returns to lay near this coarse shelter; it then 

 takes each egg and buries it in the heap, the larger 

 end uppermost. It places a new layer above, and 

 quits its labor for good. Incubation takes place 

 favored by the uniform heat of this decomposing 

 mass, hatching is produced, and the young emerge 

 from their primitive nest. 



Birds are not alone in constructing temporary 

 dwellings in which to lay their eggs; some fish are 

 equally artistic in this kind of industry, and even 

 certain reptiles. The alligator of the Mississippi 

 would not perhaps at first be regarded as a model 

 of maternal foresight. Yet the female constructs a 

 genuine nest. She seeks a very inaccessible spot in 

 the midst of brushwood and thickets of reeds. With 

 her jaw she carries thither boughs which she arranges 

 on the soil and covers with leaves. She lays her eggs 

 and conceals them with care beneath vegetable re- 

 mains. Not yet considering her work completed, 

 she stays in the neighborhood watching with jealous 

 eye the thicket which shelters the dear deposit, and 

 never ceases to mount guard threateningly until the 

 day when her young ones can follow her into the 

 stream. 



A hymenopterous relative of the bees, the Mega- 

 chile, cuts out in rose-leaves fragments of appro- 

 priate form which it bears away to a small hole in a 

 tree, an abandoned mouse nest or some similar cavity. 



