INTRODUCTION. CXXXl 



Here and there refractory species have been encoun- 

 tered, which it has been difficult to range under any con- 

 stituted group ; they have been associated (provisionally) 

 with the forms with which they seem to have the largest 

 amount of affinity. 



A word in conclusion as to the nomenclature. The stu- 

 dent will note many changes, and will regret (as I do) the 

 loss of old and familiar names. But the changes, such as 

 they are, have been made, not wantonly, but after careful 

 examination, in obedience to a principle which I believe to 

 be, on the whole, eminently conducive to the interests of 

 science. To the new generation, we must remember, they 

 will bring no regrets, but only the gain of a more uniform 

 and stable system. 



For the rest, I shall be well content if this revision of 

 the older classification should be a step towards the reali- 

 zation of a natural system, and a help towards a yet fur- 

 ther step in advance. 



NAME OF THE CLASS. 



With reference to the name of the Class, it seems almost 

 vain to hope for uniformity of practice. The continental 

 zoologists universally (I believe) employ Ehrenberg's de- 

 signation, Bryozoa', the English generally, and some 

 Americans at least, give the preference to J. V. Thomp- 

 son's name. The point has often been discussed, but with 

 little result. The arguments on each side, however satis- 

 factory to those who use them, do not diminish the amount 

 of disagreement. The contrasted opinions have, indeed, 

 their geographical range, and are subject to very strin- 

 gent laws of distribution. 



It seems necessary, however, to re-state the grounds on 



