264 DOCTRINE OF EVOLUTION 



the winter months. In other species seeds are procured 

 and stored in underground granaries. The leaf-cutters 

 are forms which grow food suppHes of fungi in sub- 

 terranean mushroom gardens ; the compost consists of 

 cuttings brought from the leaves of bushes by mj^iads 

 of workers, whose processions are guarded by larger- 

 headed soldiers of several ranks. In the honey-ants of 

 Colorado and tropical America certain individuals pass 

 their time suspended from the roof of a large nest- 

 chamber, where they receive the sweet juice brought 

 in by the workers. They serve as animated preserve 

 jars, distended sometimes to the size of a grape with the 

 communal stores of food, which they return to the 

 workers when external sources of food may fail. Finally 

 there are the slaveholding species which conduct 

 forays upon the nests of other forms, to procure the 

 young of the latter, which grow up in their captors' 

 nests and serve them as nurses and masons and foragers. 

 So long has this custom been established that some 

 slaveholders are entirely unable to feed themselves, 

 and would die out if their slaves failed to support them. 



Let us pause at this point to summarize the results of 

 the foregoing analysis, in order that we may approach 

 the biological study of human associations with definite 

 and clear conceptions of the fundamental laws control- 

 ling living communities of all grades. 



We have dealt mainly with Amoeba, Hydra, and the 

 ant-community which exemplify three somewhat dis- 

 tinct types of organic individuality. Some of the 

 transitional forms have been specified to show how the 



