220 Professor Smith's Conspectus of the Diatomacese. 



cation would put the latter. Why, we actually find Arachnoidiscus 

 along with Navicula ! in W. Smith's classification, the only point 

 of resemblance being that both are free : for same reason we may 

 associate an ant and an antelope. In my own classification, which 

 is not so wholly artificial but that it is based upon the position and 

 character of the " Raphe," or medium line, into three tribes, Arach- 

 noidiscus, not so very unlike Melosira in S. V., is associated with 

 that genus, and also as to its being free I may mention that chains 

 of three or four individuals are not uncommon. Again, some doubt, 

 both on the part of Mr. Kitton and Captain Lang, appears to exist 

 about the propriety of my union of Triceratium and Amphitetras 

 with Biddulphia (which, by the way, is only in part, as all those 

 forms, without processes, go with the Coscinodisceas). As Captain 

 Lang makes a point here, that Biddulphia coheres, forming a zig- 

 zag filament, and the others, a straight one, if any (preferring the 

 natural (?) classification of W. Smith, who puts Biddulphia with 

 Diatoma! and Triceratium and Amphitetras with Navicula!!!) I 

 commend to him Mr. Eoper's little woodcut, ' Trans. Mic. Soc.,' 

 vol. viii. p. 57, where he will find Triceratium zigzag, and Tuffen 

 West's representations of Biddulphia Arinta, PI. XLV., S.B.D., 

 where he will find this diatom forming a straight filament. End- 

 less anomalies and confusions result from considering these evanes- 

 cent conditions as of value. Mr. Kitton's remarks about Campylo- 

 discus* are reiterated by Captain Lang, though he is not so decided. 

 That Campy lodiscus has, in some cases, crossed valves, is true ; I 

 think it will be hard to show that it has in all. I shall not shrink 

 from extending a genus, because, forsooth, the number of species 

 will become inconveniently large ; to found a new genus on such 

 grounds would be far from natural. Captain Lang is right that 

 the Table of Species will involve a vast amount of labour and 

 trouble. In the next number of the ' Lens ' I give the species of 

 the genus Amphora. Unless I am aided by generous sympathy 

 and kind advice, I know I must go hesitatingly, and often erro- 

 neously forward. Most thankful shall I be for any original speci- 

 mens, memoirs, or other assistance, in the arduous task which 

 involves, not only the consideration of every hitherto (so far as I 

 know) named species, but a classification, with descriptions, figures, 

 and index. 



I was not before aware of Dr. McDonald's paper in the 

 January number of the 'Annals and Mag.,' 1869, nor have I yet 

 seen it. If I have done him injustice by any seeming neglect, I 

 beg to apologize. As for Dr. Pfitzer's classification on the method 

 of reproduction, I only know it through the abstracts published in 

 the journals ; that method of classification I long ago tried and 

 abandoned, as he will be obliged to. With all the enthusiasm of a 

 novice I fancied here was the key to unlock the mysteries of the 

 * ' Grevillea,' vol. i„ p. (33. 



