ABSTRACT
To those who in this day advocate the non-existence of species it must doubtless seem but a profitless task and an illusory effort to try, by a definition or diagnosis, to fix a boundary to that which they assert is only imaginary ; but they who defend this bold and sweeping hypothesis, however justly celebrated some of their names may be, are, I imagine, still in the minority, though that circumstance, I admit, is in itself far from proving that they have not truth on their side. But, as far as I can at present see, their case, however plausibly put, seems far indeed from proven; but, on the contrary, geological data, and our experience of the world around us, seem hitherto, at least to my humble judgment, to combine in subverting and disproving it. Species, as usually understood—some more, some less variable—I, for the present at least, conceive to exist, and not less amongst the microscopic forms than amongst those of larger growth.
‘Natural History Review,’ 0. S., vol. vi, p. 464; ‘Proc. Nat. Hist. Soc. Dub.’; also ‘Quarterly Journal of Microscopical Science’ 0. S., vol. viii, p. 79) “On a New Genus and Species in the Desmidiacese, with some remarks on the Arrangement of the Genera and Species of Mierasterias and Euastrum,” by the Rev. R. V. Dixon, A.M., Ex. F.T.C.D.
Since this paper was read I have had an opportunity, through the kindness of my friend, Mr. W. Keay, of examining a gathering made near Duudee, in which M. denticulata occurred, and in no point did his specimens differ from that species collected in this country; and the same might be said of the other forms therein common to Scotland and Ireland.—W. A.
