302 THE WORLD OF LIFE 



us hope that the twentieth century will see the rise of a truer 

 religion, a purer Christianity; that the conscience of our 

 rulers will no longer permit a single man, woman, or child to 

 have its life shortened or destroyed by any preventable cause, 

 however profitable the present system may be to their employ- 

 ers; that no one shall be allowed to accumulate wealth by the 

 labour of others unless and until every labourer shall have re- 

 ceived sufficient, not only for a bare subsistence, but for all the 

 reasonable comforts and enjoyments of life, including ample 

 recreation and provision for a restful and happy old age. 

 Briefly, the support of the labourers without any injury to 

 health or shortening of life should be a first charge upon the 

 products of labour. Every kind of labour that will not bear 

 this charge is immoral and is unworthy of a civilised com- 

 munity. 



The Teaching of the Geological Record 



But this is a digression. Let us now return to a consid- 

 eration of the main features of the course of life-development. 



The first point to w^hich our attention may be directed is, 

 that the necessary dependence of animal life upon vegetation 

 is the cause of some of the most prominent and perhaps the 

 most puzzling features of the early life-world as presented to 

 us by the geological record. In the Palaeozoic age we already 

 meet with a very abundant and very varied aquatic life, in 

 which all the great classes of the animal kingdom — sponges, 

 zoophytes, echinoderms, worms, Mollusca, and vertebrates — 

 were already fully differentiated from each other as we now 

 find them, and existed in considerable variety and in gi'eat 

 numbers. It is quite possible that the seas and oceans of those 

 remote ages were nearly as full of life as they are now, though 

 the forms of life were less varied and generally of a lower type. 

 But, at the same time, the animal life of the land was very 

 scanty, the only vertebrates that occupied it being a few Am- 

 phibia and archaic reptiles. There were, however, a consid- 

 erable number of primitive centipedes, spiders, Crustacea, and 



