BUBLnr KATUBAL HI8T0BT SOCIICTT. 199 



Mb. W. Abcheb read the following — 



DESCRIPTION OF TWO NEW SPECIES OP STAUBASTBFM. 



In these days of cancelliiig from oiir lists, and their consolidation with 

 others, of numerous species, or reputed species, in the various walks of Na- 

 tural History, — and tills, no doubt, in many cases, with much reason, — it 

 may appear unjustifiable rashness and temerity on my part to come for- 

 ward for the purpose of describing the following two new forms to be added 

 to our lists of Desniidiac®. But in a more extended point of view, in 

 regard to what is a species and what is not, it seems to me that natu- 

 ralists are prone to err in one of two directions : they either restrict the 

 number of species in their lists within too narrow limits, or inordinately 

 increase their number by giving a name and specific rank to almost every 

 variation which they encounter. On the one hand, because, between 

 two hitherto recognised distinct, but allied species, there are occasionally 

 found forms, as it were intermediate, connecting them, it is assumed that 

 these two original forms must necessarily make but one species. On the 

 other hand, those naturalists might possibly be not wanting who would 

 feel inclined to consider not only the two original, but also one or seve- 

 ral of those intermediate forms, as themselves species. Both extremes, 

 as it seems to me, may be wrong. Might it not be expected to be the 

 case that the limits of variation of each of the two original species, so 

 nearly allied, might, so to speak, so touch each other at the margin, as 

 to seem to unite them together, and give rise to the assumption, always 

 plausible, but perhaps not always correct, that one of the original species 

 could (and does), by a series of transitions, pass into the other ? If any 

 one species become modified, is it not to be expected that the characters 

 of the most nearly allied form, and not those of one remote in aflfinity, 

 will be those which, to a greater or less degree, it will be likely to si- 

 mulate ? Under this hypothesis, the two original forms would still 

 justly be considered true and distinct species— in contradiction to the opi- 

 nion of the former class of naturalists — while the forms intermediate 

 would be but variations (perhaps but of a temporary or local nature), some 

 derived from one species, some perhaps from the other, and could by no 

 means be looked upon as true species — in opposition to the views of the 

 latter class of naturalists. I do not mean to intimate, when a hitherto 

 acknowledged species is rejected, that I imagine the step always to be 

 an erroneous one, for he who successfully demolishes the spurious claims 

 of a mere book-species does Science a good service ; but it seems to me 

 that what I have tried to express is a state of things, the possibility of 

 the existence of which, by those who are anxious to suppress species, 

 may sometimes be lost sight of or ignored. 



There can be no doubt, however (and especially amongst microsco- 

 pic forms), that our lists ai-e more or less incumbered with the redun- 

 dant names of false species, which further research will doubtless even- 

 tually prove. Many forms which now pass under distinct names may 

 hereafter be found not worthy to take specific rank in our systems. 

 And here it is that the difficulty lies. In order to prove the identity of 

 two reputed species, over which there hangs a doubt, not only must the 



