vi SEXUAL DIMORPHISM 



expedition, provided only with notebooks and drawing 

 materials, and strictly forbidden to kill, preserve, or bring 

 home a single specimen, might obtain results of the greatest 

 value to science. 



It is surprising that our scientific menageries have not 

 added more to our knowledge in the direction to which I 

 refer. It is true that many interesting and valuable obser- 

 vations have been made, but as the description of the 

 behaviour of a living animal adds so much less to a man's 

 reputation than an anatomical or systematic research, the 

 study of habits makes slow progress. 



If the incompleteness of my work in this sense should 

 appear to be a reason for deferring its publication, I would 

 plead a hope that in its present state it may stimulate and 

 suggest investigations, which are not likely to be undertaken 

 until the importance of their object is realised. 



But I cannot claim that my book contains all the informa- 

 tion that has been recorded, or that I have fully considered that 

 information. The reason of this is that, owing to the pressure 

 of other duties, I was unable to devote more time to it. If I had 

 not published it now as it is, it might never have been published 

 at all a contingency which, whatever my fellow-zoologists 

 may think, I at least could not accept with equanimity. 



Incomplete as it is, the book would have been much more 

 so but for the generous aid of many able friends. Mr. E. W. L. 

 Holt supplied me with valuable material for the Chapter on 

 Fishes, and also assisted by superintending the preparation of 

 some of the illustrations. Mr. Kupert Vallentin allowed me 

 to make use of the unique photographs from the living 

 elephant seal which he took with his own camera in the 

 Falkland Islands. To Dr. Hans Gadow I am deeply indebted 



