CHAPTER I 



INTRODUCTORY: THE WORMS: CONVOLUTA ROS- 

 COFFENSIS AND CONVOLUTA PARADOXA: THEIR 

 HABITS AND HABITATS. 



BIOLOGISTS who devote themselves to the investi- 

 gation of the life histories and life processes of the 

 lower animals are apt to encounter the criticism: 

 why expend pain and labour on insignificant creatures 

 when so much remains to discover with respect to 

 the higher animals, including man himself? 



This perfectly legitimate criticism admits of a con- 

 clusive reply and, since it is possible that a question 

 of the kind may arise in the mind of anyone taking 

 up this book, it shall be answered forthwith. The 

 reply may take one of three forms. In the first place, 

 it may be urged that the most important modern 

 biological discoveries have resulted from researches 

 into the life histories of the lower organisms. Modern 

 surgery relies for much of its technique on the results 

 of investigations into the physiology of the bacteria. 

 Yet more recently, the experimental elucidation of 

 the life-histories of the protozoa the lowest group of 



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