THE ANIMAL KINGDOM 1299 



merits; that is, into cells* which, by their metamor- 

 phoses, give rise to tissues. In all other animals, on 

 the other hand, the protoplasmic mass, which con- 

 stitutes the primitive body, is converted into a mul- 

 titude of cells, which become metamorphosed into 

 the tissues of the body. 



For the first of these divisions the old name of 

 Protozoa may be retained; for the second, the title 

 of Metazoa, recently proposed by Haeckel, may be 

 conveniently employed. 



The subjoined synopsis indicates the general rela- 

 tions of the different groups of the animal kingdom. 



Those who are familiar with the existing condi- 

 tion of our knowledge of animal morphology will be 

 aware that any such scheme must needs, at present, 

 be tentative and subject to extensive revision, in cor- 

 respondence with the advance of knowledge. Nor 

 will they regard it as any objection to the scheme of 

 classification proposed, that the divisions sketched 

 out may be incapable of sharp definition the con- 

 stant tendency of modern investigations being to 

 break through all boundaries of groups, and to fill 

 up the gaps between them by the discovery of tran- 

 sitional forms. In the place of assemblages of dis- 

 tinctly definable groups, which it has hitherto been 

 the object of the taxonomist to define and co-ordi- 

 nate in precise logical categories, we are gradually 

 learning to substitute series, in which all the modi- 

 fications by which a fundamental form passes from 

 lower to higher degrees of organic complication are 

 summed up. 



* The term "cell" is used here in its broadest sense. 



