PREFACE. 



to apparently trivial })articulars, it must be remem- 

 bered that it is precisely in these that we often meet 

 with the most suggestive genealogical hints, and 

 discover the earliest stages of that process of minute 

 progressive change which has resulted in such richly 

 varied modification of organic form. 



It is needless to say a word in these days on be- 

 half of the careful study of varieties; it has been my 

 endeavour in the present work to exhibit them in 

 their faint beginnings, as well as in their fuller de- 

 velopment. 



Our attempts at the Classification of the Polyzoa 

 must still, I fear, be in large measure provisional ; 

 but it is certainly time that the purely artificial 

 methods of the past should give place to a system 

 aiming, at least, to represent the natural relation- 

 ships. 



The arrangement which I have adopted has many 

 points of agreement, so far as general principles 

 are concerned, with that which we owe to the able 

 Swedish zoologist. Professor Smitt ; and I desire 

 here to acknowledge my many obligations to his 

 suggestive writings. Though its details may be open 

 in some respects to criticism, it will, I trust, help the 

 student towards a truer conception of the relation of 

 the difterent forms and the significance of their mor- 

 ])hological characters. 



Whatever changes of system may come, I may be 

 allowed to hope that the minute and careful study of 

 the individual species, of which this ' History ' is the 

 record, may retain some permanent value, and may 



