XOTES AND MEMORANDA. 331 



Tvhich have appeared in this Journal, they are still most 

 valuable as the work of an observer so thoroughly conversant 

 with the distinctive features and characteristics requisite to 

 be especially pourtrayed in relation to individual forms. 



The author precedes the Classification and Descriptive 

 Enumeration of the species by a short Introduction, in 

 which he speaks of the Motion, the Structure of the Cell, 

 the Reproduction, the Classification, and the Distribution 

 of the Diatomaceee. 



As to Classification, the author prefers partially to follow 

 Heiberg ('DeDanske Diatomeer,' Copenhagen, 1863) rather 

 than Pfitzer {' Ueber Bau und Entwickelung der Bacillaria- 

 ceen,' Bonn, 1871, in Hanstein's ' Botanische Abhand- 

 lungen ') ; but, opposed to Heiberg, he prefers to keep 

 together the forms with cuneate outline as a special group 

 (in place of associating, as does Heiberg Meridion, and 

 Asterionella with Fragiliariese, as " Fragiliarieae Cuneatee ;" 

 Podosphenia with Striatellese, as " Striatellese Cuneatse ;" 

 Gomphonema and Cocconeis with Naviculeae, as " Naviculese 

 Cuneatae;'' and he also prefers still to attach more importance 

 than does Heiberg to the circumstance as to whether the 

 frustules are free, or attached by a gelatinous cushion, or by 

 a more or less elongate stipes, or concatenated in chains, or 

 enveloped in more or less definite mucous tubular fronds : 

 he rather recognises these varied modes of growth as of generic 

 value, which is perhaps in some cases questionable. But to 

 decide between the diverse opinions of the two authors 

 would require a very lengthened and repeated study of the 

 organisms in the living state, from period to period and 

 season to season — afield of observation which, on the whole, 

 seems too much neglected by diatomists. The advantage, 

 to beginners at least, of the author's Avork, containing as it 

 does such a great mass of the accumulated experience of an 

 able observer, would have been enhanced by analytical keys 

 of the groups and genera, to form, as it M-ere, finger-posts 

 for the guidance of strangers in this very extensive — possibly 

 to them wholly imknown — territory, albeit the adept could 

 find his way at once. Such, it is understood, Mr. O'Meara 

 will prepare and append to the second forthcoming part of 

 his work, Avhich is expected to be ready to appear, through 

 the same channel, in about a year, and no doubt diato- 

 mists will look forward to it with impatience. The mode 

 of breaking up of the long genus Navicula (with Avhich Mr. 

 O'Meara combines Pinnularia), and the grouping of the 

 various species, betokens the long and careful study of the 

 author. It is questionable, upon coining to the individual 



