INTEODUCTORY. 3 



than want of space that make it necessary for a num- 

 ber of people to have a common home and live together 

 under one roof ; where there is danger to he feared 

 from attacks by hostile tribes, or where mutual help or 

 great economy of labor can be secured, as in the case 

 of soldiers in their barracks, or workmen employed in 

 some large factory, the same banding together of fami- 

 lies is to be found. 



This association of numbers of individuals into 

 societies, much more closely bound together by ties 

 of mutual interest than are any composed of human 

 beings, is found to some extent among birds and mam- 

 mals, but oftener and in far greater perfection among 

 insects. 



Australian sea-horse. 



