GENERAL ZOOLOGICAL FACTS AND THEORIES 301 



The gregarious habit is also of value for offense, as in the case 

 of wolves that hunt in packs, and not infrequently the weak band 

 together and attack the strong, for example, the swallows that 

 unite to drive away birds of prey. Combined activities of other 

 kinds also occur; certain beetles help one another to bury small 

 dead animals in which their eggs are laid ; the monarch butterflies, 

 as well as most of the birds, congregate in the autumn, and migrate 

 southward together. 



The steps in the progress toward a social life are extremely 

 interesting (268). 



(1) In the lowest animals, the Protozoa, there are certain spe- 

 cies, like Volvox (Fig. 46, p. 97), that consist of colonies of cells 



ambling the early stages in the development of a Metazoon 

 (see p. 107). 



(2) Some of the many-celled animals of almost every phylum 

 form colonies, which contain individuals physically different 



tuse of their functions, but all referable to a common type 

 id all mutually dependent; for example, the Portuguese man- 

 )f-war among the Ccelenterates (Fig. 67, p. 142). 



(3) The love of mates constitutes a third step in social prog- 

 Many of the higher Metazoa, such as insects and fish, 



)ut especially birds and mammals, mate and become mutually 

 lelpful. 



(4) The love of mates leads to family life, as exemplified by 

 its, bees, birds, beavers, and many other animals. 



(5) And finally society, which is the combination of families, 

 ^presents the most advanced stage of social life. 



In conclusion we may say with Kropotkin, " While fully 

 Imitting that force, swiftness, protective colors, cunning, and 

 idurance of hunger and cold, which are mentioned by Darwin 

 id Wallace as so many qualities making the individuals or the 

 >ecies the fittest under certain circumstances, we maintain that 

 inder any circumstances sociability is the greatest advantage 

 the struggle for life. . . . The fittest are thus the most socia- 

 animals, and sociability appears as the chief factor of evo- 



