vi PREFACT. 



nature of life and organisation by concentrating on the active 

 response of the animal, as manifested both in behaviour and 

 in morphogenesis, particularly in the post-embryonic stages, 

 than by giving attention exclusively to the historical aspect 

 of structure, as is the custom of " pure morphology." I 

 believe we shall only make progress in this direction if we 

 frankly adopt the simple everyday conception of living things 

 which many of us have had drilled out of us that they are 

 active, purposeful agents, not mere complicated aggregations 

 of protein and other substances. Such an attitude is prob- 

 ably quite as sound philosophically as the opposing one, but 

 I have not in this place attempted any justification of it. I 

 have touched very lightly upon the controversy between 

 vitalism and materialism which has been revived with the 

 earl\- years of the present century. It hardly lends itself as 

 yet to historical treatment, and I could hardly hope to 

 maintain with regard to it that objective attitude which 

 should characterise the historian. 



The main result I hope to have achieved with this book 

 is the demonstration, tentative and incomplete as it is, of 

 the essential continuity of animal morphology from the days of 

 Aristotle down to our own time. It is unfortunately true that 

 modern biology, perhaps in consequence of the great advances 

 it has made in certain directions, has to a considerable 

 extent lost its' historical consciousness, and if this book helps 

 in any degree to counteract this tendency so far as animal 

 morphology is concerned, it will have served its purpose. 



I owe a debt of gratitude to my friends Dr James F. 

 Gcmmill and Prof. J. Arthur Thomson for much kindly 

 encouragement and helpful criticism. The credit for the 

 illustrations is due to my wife-, .Mrs Jehanne A. Russell. 

 One is from Nature; the others are drawn from the original 

 figure's. 



E. S. R. 



Cmisr.A, 



