ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 317 



their frequency. The same lists are also shown in tabular form. The 

 second part of the report is devoted to special observations on the most 

 interesting species, collected with a few exceptions between 65° S. lat. and 

 70° S. lat. The species are discussed in great detail and figured, and new 

 ones are described. The third part is entitled "General Observa- 

 tions," and in it the author discusses distribution, in depth, seasonal, 

 and geographical. An examination of the samples of the various stations 

 shows that the different groups of stations may be distinguished by their 

 respective floras. The various groups are discussed from this aspect, and 

 from the point of view of depth. The author then summarizes his con- 

 clusions on the characters of the Antarctic plankton flora, and gives a 

 comparison of the floras of the Arctic and Antarctic regions. The 

 phytoplankton consists principally of Peridiniales, Diatomacefe, and a few 

 Schizophyceffi, the last being a new record for the Antarctic. Peridiniales, 

 in sharp contrast to the Arctic regions, are very rare in the Antarctic. 

 Ceratium is entirely absent, and Peridinium is only represented by a few 

 small species, among them being P. joeUucidum, which is common to the 

 two regions. Diatomaceas are the principal constituents of the Antarctic 

 flora. In the present paper the number of species added to the already 

 recorded diatom flora of the Antarctic brings the total up to about 

 220 species, of which six are described as new. The characteristic 

 species is Corethron valduu'se, which occurs in every sample except 

 one, and in many of them is of great abundance. It is essentially a 

 summer species, abounding from December to the end of April ; very 

 rare from May to the end of October. Coscinodiscus flourishes from 

 October to January, the spring-time. The same may be said of 

 Eucampia antardica and Biddidphia striata ; while B. poJijmorpha and 

 MeJosira Sol are more autumn and winter species. The author discusses 

 shortly regional variations. A detailed comparison of the Arctic and 

 Antarctic floras shows that eleven genera are common to both regions, 

 and thirty-one species, of which latter all, except five or six, are more or 

 less cosmopolitan. 



Pinnularias.* — C. Jones writes on the Secondaries or dotted structure 

 in Pinnularise. He discusser shortly the views of H. J. Slack and the 

 photograph of Pinmdaria nobilis produced by T. A. O'Donohoe, and 

 then gives his own conclusions on the subject as the result of an 

 examination of his own material. He is of opinion that finding the 

 dots is not a matter of resolution as ordinarily understood, but rathei 

 of rendering them more conspicuous, except, perhaps, in some of the 

 smaller valves. The dots are not immediately connected with the costfe, 

 as Slack and others appear to have assumed. When viewing a valve in 

 the ordinary way — that is, with its outside or convex side uppermost — 

 it appears that there is a dotted membrane under the costfe, and a non- 

 dotted, if not structureless, membrane over the costas, and that the dots 

 are generally hidden by this upper membrane, unless special means are 

 taken to render the dots conspicuous. This dotted membrane appears 

 to be attached, at least in some cases, to the girdle. This accounts for 

 its absence from some valves. On the other hand, it is sometimes 



♦ Journ, Quekett Micr. Club, xiii. (1916) pp. 107-10 (figs.). 



