ARCHER^ OX A NEW SPECIES OF MICRASTERIAS. 237 



constrained to suppose a distinct species, may not in truth 

 be onh' a phase of variation, or of development, or an '^alter- 

 nation of generation " of the actual species, whose extremes 

 of variation, or whose life history, are as yet unknown. 

 Now, in the family of Algse, to which I liave the pleasure 

 to make a small addition (the Desmidiaceai), this whole 

 course of development has not been traced, except in two 

 or three instances; whilst in many species even the cha- 

 racteristic form of the sporangium following conjugation, 

 which here represents the reproductive condition, is unknown, 

 although frequentl)^ met with in other species. But even in 

 regard to the numerous Desmidiaii species which have not 

 been so traced up to the development of new individuals, but 

 only so far as the conjugative act itself, and the formation 

 and perfecting of the resultant sporangium (frequently, 

 indeed, met with in certain species), I would draw attention 

 to a circumstance I am disposed to look upon as an almost 

 unimpeachable argument as to their actual specific distinct- 

 ness. I allude to the fact that, no matter how numerous or 

 how few the fronds, the conjugating specimens always con- 

 jugate like form or species with like form or species — the 

 abundant with their abundant neighbours of the same species, 

 the rare seeking out the rare of the same species, and over- 

 looking the possibly more numerous specimens of a perhaps 

 closely allied species. And it is marvellous, however few a 

 certain species may be amongst the mass of others, by what 

 attraction or force these little vegetable organisms, not en- 

 dowed with a special locomotive power, are impelled to seek 

 only their fellows Avhen about to conjugate, avoiding other 

 more abundant species, themselves even, perhaps, conjugating 

 with each other at the time. The same may be said to be 

 true of other Conjugatae. Such, at least, is my own ex- 

 perience ; yet, at the same time, that a Injbrid (so to speak) 

 might occur amongst these lower Algtc, as well as amongst 

 higher plants, is perhaps not impossible ; but even if it did, 

 it does not appear to me that such a circumstance Avould 

 weigh as an argument against the existence of actual species 

 in this family. But, further, I believe if the development of 

 new individuals from a generative act has been traced in a few, 

 even in one species, and the result of such investigations has 

 been to prove that the so observed parent form or species, 

 after passing through its reproductive stages, gives birth to 

 its own complete likeness, that its specific rank has, to all 

 intents and purposes, been established. Now, this has been 

 done by Professor de Bary * in regard to at least two species 

 * ' CJutersucbungen iiber die Familie der Conjugaten/ t. vi, p. 52. 



