PREFACE 



vn 



form. Many references to be found scattered through the 

 volume are due to his suggestion, and for some he is 

 wholly responsible. I have to thank Mr. W. E. Hoyle, 

 of The Owens College, for help in a number of technical 

 points, Miss M. V. Vernon for help in the preparation 

 of the MS., and several friends for aid in experiments. 

 Last, but not least, I am under a special obligation to 

 Messrs. Jennison, proprietors of the Belle Vue Gardens, 

 Manchester, for their courtesy in placing their great 

 collection of animals at my disposal for the purpose of 

 my investigations. 



