Algae. 135 



West, W. and G. S. West. A further Contribution to the 

 Freshwater Plankton of the Scottish Lochs. (Trans. Royal 

 Society of Edinburgh. XLI. part. III. p. 477—518. 7 plates. i906.) 



The present paper is a continuation of an investigation begun 

 by the authors in 1901 — 1902, and deals with the results of a visit 

 to the north-west of Scotland in the summer of 1903. Material was 

 collected from more than twenty of the lochs in Perth, Inverness, 

 Ross, and the Outer Hebrides. The collections were made in the 

 ordinary manner by Silken tow-nets, about 9 inches diameter at the 

 mouth , and the material was mostly preserved in 4 per cent formalin. 

 A detailed account is given of the plankton of the 24 lochs investi- 

 gated followed by a table of results, which includes algae from 

 Loch Tay, Perthshire and from Loch Laxadale, Harris, 

 previously recorded by the authors; as also collections made bj'- 

 Mr. J. Murray from lochs in Sutherlandshire and Inverness. 

 The Peridineae were worked out by Mr. Lemmermann of Bremen, 

 who describes a new species, Peridiniiini Westii. 



In a "Systematic account of the more important algae of the 

 plankton" the most interesting of the algae found are dealt with. 

 Many of these belong to the family Desmidiaceae , in which the 

 Scottish plankton is remarkably rieh. Three species , y'\z. , Staiirastrum 

 inelegans, S. submidibrachiatum , and Desmidium occidentale and a 

 number of varieties are here described and figured for the first 

 tirae, most of them having been found in Loch Fadaghoda, Lewis. 

 The foUow ing rare Desmids are here recorded for the first time from 

 the British Isles: Gonatosygon aciäeatum Hast., Hyalotheca indica 

 Turn., Micrasterias WalUchii Grün., Staiirastnini sublaevispinum^ .%i 

 G. S. West, and S. Tohopekaligense Wolle, var. trifitrcatum W. & 

 G. S. West. A new brown alga, Phaecocciis planctoniciis , occurred 

 in several of the lakes examined, and the occurrence of Coelastrum 

 Monis W. & G. S. West is very interesting. An undescribed genus 

 of the Protococcoideae , Actinobotrys , occurred in quantity in some 

 of the lakes, and a few specimens of Pleodorina californica Shaw, 

 where observed from Loch Fadaghoda. Botrycocciis protuberans 

 is also a well-marked new species. Of the Diatoms, i?///s'oso/^H/«m^ws/s 

 H. L. Sm. var. morsa and Fragilaria Crotonensis Kitt. var. contorta 

 are worthy of mention. 



After some general remarks on Scottish Phytoplankton , a sum- 

 mary is given of what is know at present of the phytoplankton of 

 the inland waters of the west of Scotland: 



1. The quantity of plankton is relatively small at any time and 

 scarcely affects the colour of the water. It exhibits little periodicty, 

 the seasonal variations being slight. This absence of any marked 

 Variation in character is to be attributed to the relatively slight 

 changes in the temperature of the surface waters at different seasons. 



2. The greater part of the phytoplankton consists of Chlorophyceae, 

 and the major portion of these belong to the Conjugatae. Most of 

 the filamentous algae of the plankton are Conjugates. 



3. The plankton contains a rieh Desmid-flora. 



4. This Desmid-flora owes its existence to the Older Palaeozoic 

 and Precamban formations of the areas in which the lakes are situ- 

 ated. This rieh Desmid-flora is not an isolated phenomenon peculiar 

 to the plankton of the Scottish lochs, but it is also found in the 

 plankton of those lakes of the English Lake District, N. Wales, 

 and W. Ireland which are similarl}' situated on the Older Palaeozoic 

 formations. The abundance of Desmids is due to the absence of 



