Vlll PREFACE. 



unfold, in the clearest and simplest language at 

 his command, phenomena which, as a student, 

 he has himself earnestly striven to comprehend. 

 Keenly, indeed, does he regret the deficiencies of 

 style and want of artistic combination which, but 

 too frequently, it is feared, will be found to mar 

 his pages ; believing, as he does, that for the in- 

 terpreter of nature there is a standard of literary 

 excellence not less high than that of the poet or 

 historian. 



In the select bibliographical list appended to 

 the end of the Manual will be found the names 

 of those writers from whose published works has 

 been derived that assistance which the Author 

 would now, gratefully, acknowledge. In particular 

 to Professor Huxley are his best thanks due, for, 

 without access to the original memoirs of that 

 naturalist, the second chapter, on the Class Hy- 

 drozoa, could never have been rightly completed. 

 But the Author must confess himself under deeper 

 and less formal obligations to the same philosophic 

 investigator, whose rich and suggestive seeds of 

 thought could not, from their nature, fail to fall 

 fruitfuU on the soil of any patient mind. 



From Professor Allman, also, who has done so 

 much to promote a right knowledge of the Ccelen- 

 terata, the Author has not been denied kind aid. 



