xvi PREFACE 



been kept constantly in mind; the content of the volume includes 

 the understanding and information that the intelligent layman 

 might reasonably be expected to have as a result of his experience 

 in a general course. In adhering to this idea some of the minutiae 

 of conventional Biology have been cut away. In some cases certain 

 liberties have been taken with controversial subjects and decisions 

 are stated which may be open to some differences of interpretation. 

 This is in alignment with the policy of keeping the student mind 

 clear of non-essentials in order that broad principles may stand out 

 more clearly. Laymen are not interested in disputed questions of 

 detail, nor need they be. 



For a number of reasons the writer regards the exclusive use of 

 so-called representative forms as undesirable in a course limited to 

 one year. Important among the objections is one raised by students; 

 in general, students never were and never will be interested in the 

 detail of structure of the conventional type forms, clam, frog, earth- 

 worm, crayfish, and so on. Examples and illustrations of the opera- 

 tion of principles are indispensable, however. The criticism has been 

 repeatedly advanced that in a course devoted to the development of 

 the principles of vital phenomena miuch is taught about a great 

 number of animals but very little about any one animal. The state- 

 ment, raised as a criticism, expresses a very desirable objective of a 

 general course for Liberal Arts students. The writer expresses the 

 opinion that if intensive attention is to be devoted to any one animal, 

 that animal should be the human. Thus wherever it is possible to 

 illustrate the operation of a biological principle with clarity, or 

 wherever it seems best to add information concerning the human 

 body, he has had no hesitation in making reference to Man. More- 

 over, the chief interest of the student is in his own body; he already 

 has some knowledge of its workings. Thus advantage is taken of 

 the sound pedagogical principle which relates the known to the 

 immediately related unknown. In alignment with this principle 

 and for the sake of student interest and information, the writer 



