ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 87 



last method is, however, beneficial rather than harmful to certain forms 

 of polluting algae, and may, therefore, do more harm than good. A 

 new remedy is being tried, and has so far proved successful ; but the 

 author waits for the result of further trials before detailing the process. 

 This pollution by algas renders water extremely unpleasant, though not 

 actually poisonous. 



Thames Plankton.* — F. E. Fritsch continues his investigations on 

 this subject, and compares his results with those of Schroder and Brunn- 

 thaler on the Oder and Danube respectively. In the Thames there is 

 a well-marked living plankton all the year round, while in the two 

 continental rivers there is an almost entire absence of plankton in the 

 winter. A table is given showing the periodicity of Thames plankton, 

 which may be summarised thus : mixed plankton — Melosira — Synedra 

 — mixed plankton. Aster ionella forms a minor phase during the winter 

 months. The periodic distribution of forms is not by any means the 

 same as that of the Oder or the Danube, but the author considers that 

 the periodicity of the Thames plankton may vary in different portions of 

 the river's course. The plankton of four backwaters was also examined, 

 namely, Molesey, Sunbury, Walton and Shepperton ; and the results 

 are given in the form of tables, together with a comparison with the 

 plankton of the main stream. Though there is a considerable difference 

 both in quality and quantity, the backwaters have far more of a river 

 than a pond-plankton. 



Scottish Fresh-water Plankton.j — W. West and G. S. West give 

 the result of their examination of the plankton of some lochs in various 

 parts of Scotland. They divide their paper into four sections. The 

 first is an Introduction, which deals with previous literature on British 

 fresh-water plankton, and contains remarks on the present collection and 

 the method of obtaining it. In Section II. the various lochs examined 

 are described geographically, and notes are given on the animal plank- 

 ton which was collected with the algae. Two tables follow, one of which 

 enumerates the species from eleven lochs taken in summer and autumn, 

 and the other deals with a few small collections made in the south of 

 Scotland during the spring. Section III. consists of a systematic account 

 of the most interesting species in the preceding plankton collections. 

 This is almost entirely confined to Desmids, of which six new species and 

 some new varieties are described. An interesting record is Staurastrwii 

 verticillatum Archer, no figure of which has hitherto been published ; since 

 the so-called figure of it in Cooke's BritisJi Desmids, 188G, tab. CI, fig. 3, 

 does not represent this species. The general conclusions of the authors 

 form the contents of Section IV. They find that the Scottish plankton 

 differs considerably from that of the western parts of continental 

 Europe. It is unique in the abundance of its Desmids, of which the 

 most conspicuous are of a type confined almost exclusively to the 

 extreme western and north-western shore districts of Europe and North 

 America. The commonest and most abundant species are invariably 

 those of the genus Staurastrum, principally S. Ophiura, S. Aretiseon, ar.d 



* Ann. Bot., xvii. (1903) pp. 631-47. 



t Journ. Linn. Soc. Bot., xxxv. (1903) pp. 519-50 (5 pis.). 



