638 THE POPULAR SCIEITCE MONTHLY. 



branous collarette in the form of a funnel. All these characters are 

 found in the Codosigm, monocellular Infusoria, always living isolated, 

 and are to the sponges what the Hydras are to the Siphonifera and 

 Coral Polyps. In the Anthophysm these cellules live in colonies, but 

 are yet all alike. Let polymorphism step in. Let some of the asso- 



V 

 Fig. 16.-3 and 6, Amoebae , c, d, e, sponge particles. 



ciated cells preserve the flagellif erous form, while others become amoebse, 

 a transformation which is possible, since it constitutes one of the most 

 frequent modes of reproduction of the amoeboid Infusoria, and the 

 AnthopJiysa is transformed into a sponge. The process is always the 

 same, whatever the nature of the assembled materials. Cells or polyps, 

 it always submits to the same elaboration in developing new indi- 

 viduals. The cells, once assembled in the organism, yield easily to 

 the changes required by the division of physiological labor, and form 

 various organs, although these organs never become true individuals. 

 If the individuals of a colony often descend to the state of organs, we 

 must not conclude that the organs of an animal are always individuals 

 that have lost their autonomy ; but the animal to which they belong, 

 though it may never have been an assemblage of individualities inter- 

 mediate between its own and that of cells, is not less a colony of the 

 latter subjected to the laws of evolution of all the others. Thus even 

 if we can not prove that Vertebrates and Mollusks have resulted from 

 the fusion of more simple beings that have lived an independent life, 

 they are still colonies of cells, and the law of associatio?i has conse- 

 quently lost none of its generality. 



It remains the fundamental law of development in the animal king- 

 dom, comprehending and controlling those Imos of (/roivth, of organic 

 repetition, of economy, which have been long accepted by physiolo- 

 gists, explaining hitherto mysterious homologies between different 

 parts of the body, or between different organs of the same animal ; 

 embracing in one circle all the forms of asexual generation, which are 

 its most powerful means of creation. Resting upon the law of the 

 division of physiological work, the importance of which was first 

 demonstrated by Milne-Edwards, and upon that of 2^olymorphism, 

 which without it have only a limited and indefinite meaning, conse- 

 quent on the law of division of protoplasmic masses, it has been the 

 great producer of organization, and establishes a new link between 



