134 Bibh'of/raphical Notices. 



oven what may be called a fnuul, and sdnictiinos very definite forms of 

 the individual colls theniaolves. 



" So readily ilo those specialities strike the eye, when once they have 

 been seen, tliat, kii their recurrenoo, they are at onco recofmizablo. The 

 jrenoric names AjuOct/stis, Sc/iizor/ilami/s, I'd/nitxlacti/lon, Tetidspora, Mo- 

 uosfroDia (Vfid, in ymrt), I)ic(i/(>!<p/irrriii»i, Oocardlitm, Iloniio^/wni, Xc- 

 phron/tliim, MMmcuccus, AtikistrodesiiiiiK ( lihaiihidiuni), Poliicdiiini, 

 Ci/'fto(ocru.i, Dacfi/lorncciks, Vharaciiiin, O/i/iinri/timn, '^cencde.tmiis, Pidt- 

 (tsfru)ii, CalastruDi, Sura s( rum, Ervmoxplucru, and many more, all call 

 to mind, in a moment, forms whicli, some rarely, some frequently, pre- 

 sent themselves to notice, maintain their cliaracteristics while at the 

 same time no true jifenorative process lias been discovered, and reproduce 

 themselves by diverse modes of cell-division, by zoospores, by ' brood- 

 families,' Szc. They are also found maintaininpf their characters in 

 various places ; and I think it is not readily conceival)le what varied 

 accidental concatenation of circumstances could, in so diverse localities, 

 force a certain supposed {ronidium of a lichen, or spore of a moss, now to 

 dovelope into tliis well-defined form, now iiito that. Therefore, if, on 

 tlie one hand, sucli {renera, perhaps, as C/ironroccus, GlaocapHi, Si/uccho- 

 coccus, (ilaothere (in Chroococcacvcr), and I'lcurococcu^, Ghvuci/stis, and 

 PalmcUa (iu PuhneUacece) seem, from Dr. Hicks's researches, to be in 

 jeopardy, it surely appears to me as yet that it woidd be an incautioiia 

 and too hasty conclusion to sweep away all ' Pahnellaccoi.' " 



Willi the exception of Tetraspora, Cystococcua, and perhaps 

 of Eremosphcera, the validity, for the present at least, of the 

 genera mentioned by Mr. Archer will hardly be disputed. It would 

 occupy too much space to discuss further the Puhnelhicecc and Proto- 

 coccacece ; and it is unnecessary to say more of the VoJvocinea; than 

 that the organisms composing the familj- arc here, for the first time, 

 classified in a systematic work on Alga-, and that thej' will doubt- 

 less retain their position, notwithstanding that so late as last year 

 they were placed by MM. Le Maout and Dccaisne amongst their 

 " Algoe spuria^"*. 



The order ZipjopJtjfcecv is a very natural one, comprising the 

 families Desmidiece and Zi/r/nemerr. The former of these families 

 has been made familiar to all who have paid any attention to Algao, 

 by Mr. llalfs's famous work. Upwards of twenty years have passed 

 since that work was published ; and although, of course, many new 

 species have since been described, we find little alteration of genera. 

 Stavroceras is only a form of Closterium ; Pleurot(pnlum and Triplo- 

 ceras are closely allied to Docklium ; GemlneJla is a plant of Avhich 

 little seems to be known. The genus was established by Turpin in 

 182S, in the 'Mem. du Museum d'histoire naturelle,' vol. xvi. 



The only other genus admitted by Dr. llabenhorst, and whicli wc 

 do not find in !Mr. llalfs's work, is fJo)iafu:i/f/on of Be Bary, which 

 is very near to Doc'uVmm, and is identical with Mr. Archer's Lepto- 

 ci/ntinemrt. Ten genera are placed by Dr. Rabenhorst in the 

 Zi/gnemecef. There is some confusion, as has been pointed out by 



* An important paper, by M. Pringsheim, on sexual reproduction in 

 PandoriiKi and ]^ii(Jitriii(i (two of tlie Volvocinea3) has quite recently ap- 

 peared in the ' Monatsbericlit ' of tlie IJei'lin Academy. 



t The nomenclature is not always uniform. "Zygncmeai" (p. 101, 



