238 ARCHER, ON A NEW SPECIES OF MICRASTERIAS. 



of Cosniarium, C. Botrytis and C. Meneghinii ; aud it is 

 wortliy of remark that these are both forms whose specific 

 distinctness has been called in question by some observers, 

 merely because they considerably resemble certain allied 

 species of Cosmarium. To my mind, indeed, they seem, in 

 a word, to possess only common generic characters ; and for 

 my share, while both the above species are frequent, I believe 

 there is not the smallest difficulty in distinguishing them 

 from any of their allies. Now, analogy seems to me to be 

 here an irresistible argument. Cosmarium Botrytis, as some 

 may maintain, only a variety of Cosmarium margaritiferum, 

 or of C. tetraopthalmum, or C. Brebissonii, &c. — all of vs^hich 

 they, perhaps, Avould lump together — reproduces itself from 

 the sporangium, conjugation being a true generative act, as 

 I conceive. My new Micrasterias differs by more salient 

 and striking characters from its nearest neighbouring forms 

 than do those species of Cosmarium, though it is to be men- 

 tioned that the development from the sporangium of any 

 species of INIicrasterias is unknown. It is therefore reason- 

 able to conclude that my new Micrasterias and its allies are 

 distinct species, as they certainly are abundantly distinct 

 foinns. I consider, then, if certain well-defined forms occur, 

 difl:ering from their congeners as much as do already acknow- 

 ledged species, and which may be met with the very next 

 day by other observers, it is imperative that such be duly 

 recorded under a careful description. And I would remind 

 you that this is the necessary course in all departments of 

 natural history. Constantly recurring identical forms must 

 be assumed to be the descendants of similar progenitors, 

 whatever be their intervening phases of development, of 

 alternation, or of metamorphosis ; and, as it seems to me, in 

 the absence of the various stages of the development of each 

 from the germ generated from the parent, there is no more 

 difficulty in believing such forms in the microscopic world to 

 be good species than in the case of any of the higher plants 

 or animals, in the absence of tracing their growth from the 

 ovum or germ, though in one case we may possibly know the 

 stages, and in the other we may not. 



Therefore, on all these considerations, I believe I am not 

 premature in describing the following new species of Micras- 

 terias ; and I make the preceding few observations, and direct 

 attention to the foregoing facts, for the purpose of trying, in, 

 I fear, a very inadequate manner, to meet the objections of 

 those who seem to carry a prudent precaution as to making 

 new species too far, and thus, as it appears to me, to outstep 

 the truth in one direction as much, or nearly so, as do those 



