134 Bihliographical Notices. 



even what may be called a frond, and sometimes very definite forms of 

 the individual cells themselves. 



" So readily do these specialities strike the eye, when once they have 

 been seen, that, on their recurrence, they are at once recognizable. The 

 generic names Apiocydis, SchizoeMami/s, Pcdmodactylun, Tetraspora, Mo- 

 nostroiiifi (Viva, in -part), Dicfi/osph(Frium, Oocardinm, Hormospora, Ke- 

 j)hroci/finm, Mm-hococcus, Ankistrodemius (Ithaphidiuin), Puli/cdium, 

 Ci/sfococcus, Dactiflococcus, Characitnn^ Ophioei/tium, Scencdesinus, Pidi- 

 astru)>i, Calnstfvvi, Surastnim, J^remo^ihcera, and many more, all call 

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

 sent themselves to notice, maintain their characteristics while at the 

 same time no true generative process has been discovered, and reproduce 

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

 families,' &c. They are also found maintaining their characters in 

 various places; and I think it is not readily conceivable what varied 

 accidental concatenation of circumstances could, in so diverse localities, 

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

 develope into this well-defined form, now irito that. Therefore, if, on 

 the one hand, such genera, perhaps, as C/n'oococcus, Glococopsa, Synecho- 

 coccifs, Gla'othcce (in ChroococcaccfS), and Pleiirococcus, Glmocystis, and 

 Palme/la (in P(dmcllacere) seem, fi'om Dr. Hicks's researches, to be in 

 jeopardy, it surely appears to me as yet that it would be an incautious 

 and too hasty conclusion to sweep away all * Pahnellacece.' " 



With the exception of Tetrasjwra, Cystococcus, and perhapa 

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

 genera mentioned by Mr. Archer will hardly be dis2)uted. It would 

 occupy too much space to discuss further the PahneUacece and Profo- 

 coccciccce ; and it is unnecessary to say more of the Volvocinece than 

 that the organisms composing the family are here, for the first time, 

 classified in a systematic work on Algae, and that they will doubt- 

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

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

 " Algfe spuria^"*. 



The order Zygophyceo' is a very natural one, comj)rising the 

 families De^mkliece and Zyr/nemere. The former of these families 

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

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

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

 species have since been described, Ave find little alteration of genei'a. 

 Staurocercis is onlj* a form of Chsterium ; Plearotn'.ninm and Triplo- 

 ceras are closely allied to Doddhmi ; Geminella is a plant of which 

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

 1828, in the ' Mem, du Museum d'histoire naturelle,' vol. xvi. 



The only other genus admitted by Dr. Rabenhorst, and which we 

 do not find in Mi". Ralfs's work, is Gonatozygon of De Bary, which 

 is very near to Docidium, and is identical with Mr, Archer's Lepto- 

 cystlnema. Ten genera are placed by Dr, Rabeuhorst in the 

 Zygnemece f. There is some confusion, as has been pointed out by 



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

 Pamlorina and Eudorina (two of the Volvocinere) has quite recently ap- 

 peared in the ' Mouatsbericht ' of the Berlin Academy. 



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



