444 CONCLUSION. 



deserve the names of all those who have made the Freshwater 

 Alga the object of their study. I had intended also to have 

 entered upon the consideration of the subject of classification, 

 and to have remarked on those which have hitherto been pro- 

 posed. I have been prevented from fulfilling these intentions 

 by the fact that this work has already greatly exceeded the 

 limits originally proposed for it. Should it be destined, how- 

 ever, to reach a second edition, chapters devoted to the con- 

 sideration of these two questions might, by the adoption of a 

 smaller type, be inserted with advantage. So much for the 

 omissions from the work. I would now refer to a super- 

 fluity, and beg the Reader's indulgence for what I fear, 

 without explanation, might be deemed an unnecessary in- 

 trusion on his notice, the attachment of the writer's name 

 either to each new species or to those which for the first time 

 have been referred to other genera. This was done under the 

 impression that the practice was usual and customary. 



That much still remains to be effected ere our knowledge 

 of the Freshwater A lya shall be in any thing like a complete 

 state is evident from the number of species which for the 

 first time are introduced in this work. So numerous are these, 

 and so closely do many of them approach each other, that 

 there are some, I fear, and especially such as have not made 

 the Algce their study, and who therefore are scarcely in a 

 position to declare what amount of difference is of specific 

 value, who will be ready to assert, that the species have been 

 multiplied on insufficient grounds. Let such pause ere they 

 advance such an injurious assertion, which, like all asser- 

 tions, it is an easy matter to make, but more difficult to sub- 

 stantiate ; let them first bestow upon those species the care, 

 labour, and anxiety of their founder, and then their opinion 

 will be rendered valuable, and injustice be inflicted on no 

 party. 



That superficial observers should arrive at the conclusion 

 that nearly allied species are states of one and the same pro- 

 duction is not so surprising, when we consider that the cha- 

 racters which distinguish species amongst the Alga are fre- 

 quently not very obvious or prominent, and since even men 



