ORGANIC COMMUNITIES 



99 



enveloped by the air. In the hitter reahii all the aninial 

 species consist of separate individuals which may be associ- 

 ated in intellectual communities and colonies, such as those of 

 the bees and ants, or in the herds of the herbivora or the 

 flocks of birds ; but in no case do we find them united by a 

 physical bond. It is otherwise in the sea. There, many 

 groups consist of individuals which are knit together in the 

 manner of the polyps and sponges; the several animals often 



, ,i,„ vij. 



Figure of a Sponge, such as Inhabits the Deeper Parts of the Sea 



to the number of millions combining their bodies to form vast 

 organic associations, which may build the monumental struc- 

 tures of the fringing, or atoll reefs. This structural union in 

 the life of the marine animals is paralleled on the land in the 

 plants where many separate buds are associated in a single 

 bush or tree, but none of the land animals have any such 

 union of their bodies ; such associations are possible in plants, 

 even in regions where there is winter cold, because they 

 become essentially lifeless while the frigid conditions prevail. 

 It is easy to see that it would be quite impossible for the 



