76 THE PHYSICAL KINSHIP 



others are extinct. The development of these 

 many-celled organisms (metazoa) from one-celled 

 organisms was a perfectly natural process, a 

 process which takes place in the initial evolutions 

 of every embryo. There is no more mystery 

 about it than there is about any other act of 

 association. All association is simply a matter of 

 * business.' Many-celled organisms are colonies, 

 or societies, of more or less closely co-operating 

 one-celled organisms, and they have come into 

 existence in obedience to the same laws of economy 

 and advantage as have those more modern societies 

 of metazoa known as nations, communities, and 

 states, the organised bodies of men, ants, and 

 millionaires. 



The sponges are the lowest of the many-celled 

 animals. They consist of irregular masses of 

 loosely associated cells, hopelessly anchored to 

 the sea-floor. They represent the social instinct 

 in embryo. The cells are but slightly specialised, 

 and each cell leads a more or less independent 

 existence. The sponge stands at about that stage 

 of social integration and intelligence represented 

 by those stupendous porifera which cover conti- 

 nents and constitute the ' social organisms ' of the 

 civilised world. The nutritive system of sponges 

 consists of countless pores opening from the sur- 

 face into a common canal within, through which 

 ever- waving cilia urge the alimental" waters. In 

 the celenterates the cells arrange themselves in 

 the form of a cup with one large opening into and 

 from the vase- like stomach. The unsegmented 



