236 ARCHER^ ON A NE\Y SPECIES OF MlCllASTERIAS. 



extremities, is the only speeies with which M. cupitata can 

 possibly be confounded. 15ut what constitutes an exceptional 

 character in M. Smithii is constant in the Indian species, 

 the apices being invariably truly capitate, the neck con- 

 spicuously constricted. Bvit more important distinctive cha- 

 racters are found in the much smaller number of loculi and 

 in the very obscure stride. I have examined a very large 

 number of individuals, and find that, although the loculi vary 

 Irom seven to eleven, the average number is eight or nine ; 

 Avhereas in M. Smithii the range extends from six to twenty- 

 four, according to Professor Smith. 



Description of a New Species of Micrasterias (Ag. ei 

 aliorum, non Ehr.), ivith Remarks on the Distinctions 

 betiveen Micrasterias rotata (Ralfs) «w^M. denticulata 

 (Breb.). By William Archer. 



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 growtli. 



It is true that, unless an organism can be traced through 

 its whole course of life, that is, that its development from 

 the resultant germ of a generative act, until, in its turn, by 

 another generative act, it assists to give rise to a new germ, 

 be observed — just as an oak is known to produce an acorn, 

 w'hich acorn will by and by produce another acorn-bearing 

 oak — it cannot be affirmed that any such given organism i^ 

 in reality a true species. That is, it is not proved that some 

 other form, which in the present state of knowledge we are 



