SOCIAL LIFE OF ANIMALS 



95 



relations of animals is very different from that in which 

 we have recognised the habit of forming colonies. The 

 factor which we have now to acknowledge is the love of 

 mates. This also has its history, but we shall simply 

 assume as a fact that among crustaceans and insects first, 



FIG. 25. SIPHONOPHORE COLONY. 



Showing the float (a), the swimming-bells (b) ; the nutritive, repro- 

 ductive, and other members of the colony beneath. 



(From the Evolution of Sex ; after Haeckel.) 



in fishes and amphibians afterwards, in reptiles too, but 

 most conspicuously among birds and mammals, the 

 males are attracted to the females, and in varying degrees 

 of perfection enter into relations of mutual helpfulness. 

 The relations and the attractions may be crude enough 

 to begin with, but even man may learn from the heights 

 of devotion to which their finest expressions attain. 



