VI INTRODUCTION. 



may serve as the northernmost boundary of our area, is responsible 

 for a considerable proportion of the increase ; but, so long as the 

 species belong to groups which are not essentially abyssal forms, it 

 is better to include than exclude them from a work which differs 

 widely from that of Forbes in that it is published at a time when 

 dredging at considerable depths is becoming a pastime as well as a 

 serious business. 



In the preparation of the diagnoses I hope I shall not be thought 

 to have erred on the side of brevity ; if I have been brief, I have 

 done my best to avoid being obscure. Where a writer fills page 

 after page with description he will indubitably fail if his object be to 

 make himself intelligible to others. My first object has been to 

 make every point clear, and I have not stinted myself in the use of 

 keys, artificial or otherwise, which would show what I meant. 

 If in the portion of this work which deals with the Asteroidea I have 

 in any way failed to give an accurate account of Mr. Sladen's opinions 

 or diagnoses, I must ask to be accounted innocent. I have devoted 

 many hours to his Report on the Starfishes of the ' Challenger,' but 

 in consequence of the minuteness of his descriptions of species, the 

 frequent absence of any indication of the diagnostic characters of 

 his genera, and the repeated expression of views for which he does not 

 give (I do not say does not possess) adequate reasons, the)' have not 

 been as fruitful as I could have wished. That the number of species 

 and genera which Mr. Sladen has created will be largely reduced I 

 am convinced, and I feel confident that the majority of naturalists 

 who devote themselves to the study of Starfishes will agree that the 

 species vary greatly. I cannot say how deeply I regret the extreme 

 divergence that exists between Mr. Sladen's views a well as methods 

 and my own. But I cannot assent to or approve of a mode of study 

 which practically results in the description of specimens instead of 

 the diagnosis of species, and I note with satisfaction that the 

 accomplished student of Echinodcrms at the Jardin des Plantes 

 ranges himself on the same side as myself. 



To me, indeed, and, I believe, to many others, one of the reasons 

 why the study of Echinoderms is so fascinating is that they present 

 so many and such striking variations ; these very variations are, of 

 course, the cause of the difficulty of the study, in which there is a 



