NHW VIEWS OF ANIMAL TRANSFORMATIONS. 627 



of Worms with the Articulata is apparent to every one, and we already 

 see how these same Worms are related to Mollusca and Vertebrata. 

 The theory, therefore, extends to the entire animal kingdom. 



Now, what do we mean by association ? When we say that animal 

 organisms have been in great part produced by the transformation of 

 animal societies into individuals, what do we mean by the term society? 

 Are all societies in the way to become individuals ? Many animals 

 associate together, and their societies are sometimes admirably gov- 

 erned. The social manners of dogs, antelopes, beavers, and many birds 

 are well known, while the complex and perfectly coordinated operations 

 of societies of bees, ants, termites, are the admiration of the world. 

 Do such societies ever become individuals ? Certainly not. But there 

 exist other animal societies in which the relations are closer — where 

 the individuals are not only in immediate contact but in continuity of 

 tissue with their neighbors. These societies are called colonies, but 

 the individuals that compose them are not always indissolubly united 

 together. They can separate from their companions, and live a long 

 time and affirm their independence by forming new colonies. In the 

 same zoological group of neighboring species, we find some individuals 

 that always live solitary and others always associated, as for example 

 the specially remarkable group of Polyps or Acalepha. 



One species of this group, the brown Hydra {Hydra fiisca), is 

 common in stagnant waters and even in small garden basins. It has 

 always excited the interest of naturalists and philosophers since Trem- 

 bly made known its marvelous faculties. These Hydras ordinarily live 

 solitary ; but frequently the larger individuals are seen carrying small- 

 er ones on the walls of their bodies. In a captured Hydra we can fol- 

 low their development step by step. They are at first simple swell- 



PiG. 1.— a, diagrammatic section of Hydra ; 6, Hydra viridis, showing swellings in the body-wall ; 

 c, Hydra vulgaris, with an undetached bud enlarged; d, thread-cell of the Hydra, greatly mag- 

 nified. 



ings, in the center of which there is a prolongment of the cavity of 

 the mother's body. These swellings enlarge and soon put out tenta- 

 cles, and a mouth opens in the midst of the crown formed by them. 



