xii ANIMAL BIOLOGY. [Chap. I. 



people have some knowledge of the animal world in which they 

 live and of which they form a part. But this general informa- 

 tion, useful and interesting as it is, lacks that organisation and 

 exactness which is a distinguishing mark of science. To rise 

 from general information to science, we must use the methods of 

 science, which are : (1) observation and experiment; (2) infer- 

 ence and hypothesis ; (3) verification. The beginner will, how- 

 ever, wisely rest content with repeating the observations and 

 experiments (not merely reading about them but repeating them), 

 and conscientiously verifying the inferences, of his masters in 

 science. This he must do if he is to learn science as science, and 

 not as history. To learn about .science is valuable. But to be 

 taught science itself through the direct teachings of Nature is 

 far more valuable. The student of science must learn his facts 

 at first hand, and must regard books as guides to that object. 

 Observation, experiment, and verification are to be regarded as 

 primary duties by every student of science as such. They are 

 therefore incumbent on the student of Animal Biology. 



What is the nature of those living things on the scientific 

 study of which we are now to enter? We are more or less 

 acquainted with a considerable number of very different kinds of 

 living animals, such as dogs, butterflies, worms, sea-anemones, 

 star-fish, jelly-fish, and so forth. There are also simpler and 

 more minute forms of life, with which, however, the student is 

 presumably at present unfamiliar. Taking such animals as 

 these, therefore, what is there about them to distinguish 

 them on the one hand from not-living things, and on the 

 other hand from plants 1 Let us endeavour to organise and 

 make exact the general knowledge on these questions which 

 we already possess. 



A marked characteristic of life is growth. But we speak also 

 of the growth of not-living things, of clouds, of the river in 

 flood, of crystals from solution, of tapioca grains on boiling. 

 What then distinguishes living growth ? We cannot, perhaps, 

 describe it better than by saying, (1) that it is an organic growth, 

 that is a growth of the various organs of the living animal in 

 due proportion ; (2) that it is a growth, not merely by the 



