CHAP. I The Wealth of Life n 



others with hardly any characters in common. To us these 

 many kinds of " worms " are full of interest, because in the 

 past they must have been rich in progress, and zoologists 

 find among them the bases of the other great branches — 

 Vertebrates, Molluscs, Arthropods, and Echinoderms. 

 " Worms " lie in a central (and still muddy) pool, from 

 which flow many streams. 



Lower still, and in marked contrast to the rest, are the 

 Stinging-animals, such as jellyfish throbbing in the tide, 

 zoophytes clustering like plants on the rocks, sea-anemones 

 like bright flowers, corals half-smothered with lime. In the 

 Sponges the type of architecture is often very hard to find. 

 They form a branch of the tree of life which has many 

 beautiful leaves, but has never risen far. 



Beyond this our unaided eyes will hardly lead us, yet 

 the pond-water held between us and the light shows vague 

 specks hke living motes, the firstlings of life, the simplest 

 animals or Protozoa, almost all of which have remained mere 

 unit specks of living matter. 



It is easy to write this catalogue of the chief forms of 

 life, and yet easier to read it : to have the tree of life as a 

 living picture is an achievement. It is worth while to 

 think and dream over a bird's-eye view of the animal king- 

 dom — to secure representative specimens, to arrange them 

 in a suitably shelved cupboard, so that the outlines of the 

 picture may become clear in the mind. The arrangement 

 of animals on a genealogical or pedigree tree, which 

 Haeckel first suggested, may be readily abused, but it has 

 its value in presenting a vivid image of the organic unity 

 of the animal kingdom. 



If the catalogue be thus realised, if the foliage come to 

 represent animals actually known, and if an attempt be 

 made to learn the exact nature, limits, and meaning of the 

 several branches, the student has made one of the most 

 important steps in the study of animal life. Much will 

 remain indeed — to connect the living twigs with those whose 

 leaves fell off ages ago, to understand the continual renewal 

 of the foliage by the birth of new leaves, and finally to 

 understand how the entire tree of life grew to be what it is. 



