ARCHEE— ON " TALMOGKEAn" ALGJI. 275 



paper as an example of the instability of this character. But I hardly 

 think it is a conclusive argument against the value of this character 

 to regard a plant in the varying phases of its development, and say 

 that, because such differ, that form is of no value, The phases of growth 

 should be taken, and the comparison made, at the same point in deve- 

 lopment ; for very varied phases may certainly intervene, nor does this 

 latter fact seem to me to conflict with my view. The zygospore of 

 Penium Mooreanum figured on the Plate referred to, or indeed that of 

 any other Desmid or Conjugate, or that exceptional phase of Mesotae- 

 nium, or the oospore of an CEdogonium, or even the zoospore of 

 a Cladophora, or of a Drapernaldia, &c, are not more unlike, after all, 

 to their parent or mature forms than an acorn is unlike an oak. 



Dr. Hicks further writes — " The varying forms of their divisions 

 show that their form changes very strangely. This is observable in 

 almost every Conferva, and the Desmidieas are good examples." I do 

 not quite comprehend this. If a cell of a Conferva or a Desmid during 

 division is not actually of the same figure as one fully-grown, surely it 

 attains it when the process is completed. If he means that a Conferva 

 or a Desmid during the act of division is able to change directly from 

 one form to another, I hold that this is wrong, and that there is no 

 foundation for such an assumption. 



To pass on briefly to consider the communication from Dr. Wallich 

 which I have just had the honour to read to the Society, he, while con- 

 tending for the greater or less instability of the Protophyta, the Des- 

 midieee included, does not, however, make such a demand as that just 

 adverted to. I shall, as the opportunity here occurs, venture to add a 

 word or two in allusion to Dr. "VVallich's communication, referring 

 mainly as it does to certain Desmidian forms. I have, indeed, ere 

 now endeavoured to express my own views as fully as I could on this 

 point ; therefore I shall not here attempt to dilate at any length on the 

 subject, as it would be but repetition. 



In the first place, then, Dr. "Wallich alludes to my urging the per- 

 sistence of type in the Desmidiaceoe, because they are more or less constant 

 in a given locality. On the other hand, he urges that, unless these cha- 

 racters are found to occur under erery variety of conditions he cannot 

 accept them as evidence of the persistence of type for which I have 

 contended. Now, it seems, at first sight, that it is asking somewhat too 

 much to demand that every variety of conditions should produce no 

 effect, when it is only under certain conditions that some forms are found 

 at all. But he explains that by " every variety of conditions" he 

 means " in widely remote localities." It will be admitted, I think, 

 that the West, Centre, and North of Europe are widely remote localities, 

 yet from these far apart sources the same Desmidian forms have been 

 collected, maintaining their special characters. In his lately published 

 list of Desmidieee collected in Sweden, Cleve,* while he truly enough 



* Cleve: "Bidrag till Kannedomen om Sveriges sbttvattensalger af familjen Des- 

 midieae," in "Ofversigt af Kongl. Vetenskaps-Akademiens Forhaiullingar;" Stockholm, 

 1865, p. 481. 



