INTRODUCTION 3 



animals (e.g. Volvox). Plants are divided into Cryptogams 

 and Phanerogams ; but the latter retain characters pointing 

 to their descent from the former ; and all recent study tends 

 to bring the two groups very closely together. The various 

 classes of Invertebrates present connecting links. Many 

 forms, for instance, of very different outward appearance 

 crustaceans, spiders, scorpions, etc. point to a remote 

 common ancestry, the members of which must have re- 

 sembled ringed worms. Then there are animals that cannot 

 properly be classed either as vertebrates or invertebrates 

 (e.g. Balanoglossus), and these show affinities with the fish- 

 h'ke Lancelet, the lowest vertebrate now in existence. Fishes 

 especially lung fishes show affinities with amphibians; 

 whilst amphibians are closely related to the lizard-like 

 reptile known as Sphenodon. Birds retain several reptilian 

 features in their anatomy some peculiarly so (Opisthocomus 

 cristatus, Palamedea cornuta). And the lowest forms of 

 mammals (Monotremes) reveal in their ribs and other parts 

 of their structure reptilian features not found in animals of 

 higher grade. 



Thanks to Charles Darwin, Russel Wallace, Huxley, 

 Spencer, Haeckel, Weismann, Cope, and other hard workers 

 in the fields of Biology, the doctrine that higher life-forms 

 have been evolved from lower may now be said to have 

 passed out of the region of controversy. It must, however, 

 be admitted that many subsidiary problems of descent and 

 inter-relationship remain as yet unsolved. 



All forms of life, therefore, that now abound may be 

 regarded as having come down, through inconceivably long 

 vistas of time, from an ancestry of minute one-celled or- 

 ganisms, possessing a power to vary. At some very remote 

 period this innate power became manifest in two distinct 

 directions by the appearance of minute plants and minute 

 animals. From these humble divergent forms, through 

 innumerable variations in the past, the whole of existing 

 plant and animal life has gradually obtained its present con- 

 dition of development. The power to vary possessed by the 

 earliest organisms must have been enormous. How they came 

 to be thus endowed is beyond the reach of knowledge. 



