1 8 INTRODUCTION 



breathing in air and in water, and modes of movement above- 

 ground, underground, in water, and in air. 



The subject of Development will next be dealt with, and 

 typical life-histories will be given, after which such subjects as 

 Care of Eggs and Young and Animal Homes and Dwellings 

 will receive attention. 



The lower functions of animals having been dealt with in 

 the earlier sections of the book, the higher functions will next 

 be considered, and some of the more important details regarding 

 the structure and function of Nervous System, and Sense Organs 

 will be presented. This will be followed by a section on Instinct 

 and Intelligence, activities involving the operation of the organs 

 described in the preceding section. Such matters as the migration 

 of mammals and birds, the habits of social insects (ants, bees, 

 wasps, &c.), and the "homing instinct" of certain forms, will 

 here receive treatment. 



In the remaining part of the book considerable space will 

 be devoted to the wide and interesting questions connected 

 with the Association of Organisms. The first thing here to be 

 dealt with will be the various kinds of association obtaining be- 

 tween plants and animals, such as the relation of insects to flowers, 

 ants to various plants, insectivorous plants, and galls produced 

 by insects. Next will follow an account of the chief kinds of 

 association between animals of the same species, including 

 chapters on Mating and Courtship, and on Animal Communities, 

 in so far as the last subject was not treated of in relation to 

 instinct. Different kinds of association between animals of 

 different species will be the last heading under this section, 

 and will include all the various sorts of relation known to zoolo- 

 gists, among these being Commensalism, where messmates are 

 associated; Mutualism, where two forms benefit one another; and 

 Parasitism, in which unwelcome guests prey upon a " host ". 



The concluding sections of the book will be devoted to 

 Utilitarian Zoology, Distribution in Space and Time, and 

 Philosophical Zoology. 



Under Utilitarian Zoology we shall have occasion to deal 

 with animals as the foes and friends of man, and this will naturally 

 involve some description of the chief ways of coping with foes, 

 e.g. agricultural pests, and some of the methods, e.g. pisciculture, 

 by which the usefulness of animals is enhanced. Some space 



