ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 317 



organisms which live on plankton, and may be termed ectoparasites or 

 epiplankton. He describes especially the case of Synedra investiens 

 W. Smith, which lives on the bristles and hairs of Diaixys injgmsea. 

 A list is given of epibiontic species, with their hosts, numbering ninety 

 in all, partly marine, partly freshwater. Chytridiacese, Flagellatfe and 

 Infusoria are the most frequent, Bacillariaceae and Peridiniaceae less so. 

 Of the host-plants, Schizophyceffi and Bacillariacete are more numerous 

 than Chlorophyceae and Peridiniacete. 



Atlas of Diatomacese.* — A. Schmidt's Atlas of Diatomaceaa is 

 continued by F. Hustedt after the death of A. Schmidt and of F. Fricke. 

 In former numbers the group of Centricee was figured, and Raphideae 

 of the PennatiB group. Now come Eunotia, Fragilaria, Synedra, 

 Nitzschia, Grammatophora, DenticuJa, and of marine species, Chsetoceras^ 

 Rhizosolenia, etc. A text for the atlas is also to be brought out. 



Distribution of Cyanophyceae in Soils.! — F. Esmarch has made a 

 study of the distribution of Cyanophycete on and in various soils. The 

 two problems he sets out to solve are: 1. Is the distribution of the 

 earth-inhabiting Cyanophycese dependent on the nature of the soil ? 

 Are they commoner on cultivated (manured) land than on uncultivated ? 

 2. Is the occurrence of Cyanophyceae in the lower strata of soil limited 

 to ploughed lauds, or is it universally distributed ? How can it be 

 explained ? The author describes his methods of work, the nature of 

 the various soils examined, and gives tables of the species recorded. 

 As a result he finds that as regards his first problem two factors are 

 of the greatest importance. One is the moisture-retaining capacity of 

 the soil. The other is the presence of nutritive solutions in the soil. 

 Thus on one and the same soil the frequency of the Cyanophyce^ 

 varies at different times according to these two conditions. 



As regards the second problem, the author describes his material 

 and gives lists of the species found. He then discusses the occurrence 

 of Cyanophyceae at depths of 10-2.5 c.cm. and even at 40-50 c.cm., and 

 explains how they come there and how they support life. He describes 

 his own experiments of burying certain species under 1 cm. of earth 

 and keeping them in the dark for a certain length of time. The effect 

 on the algae is described. As regards the second question — the alg» 

 found in the earth are conspecific with those found on the surface ; 

 and their occurrence in the lower strata is entirely due to their being 

 carried down by the agency of animals, infiltration of water, etc. 

 Finally, the author gives a systematic synopsis of the alga3 observed, 

 with some descriptive notes. A few undetermined species are fully 

 described and figured. 



Blanket-algae of Fresh-water Pools. J — E. L. Piatt has studied the 

 community of life that is bound up with the floating masses of 

 filamentous algae, known as " blanket-algte." She describes the method 



* Atlas der Diatomaceenkunde, Heft 73-9, taf. 289-316. Leipzig: O. R. 

 Reisland, 1913-14. See also Hedwigia, Iv. (1914) Beibl., p. 93. 

 t Hedwigia, Iv. (1914) pp. 224-73 (figs.). 

 X Amer. Nat., xlix. (1915) pp. 752-62. 



June 21st, 1916 z. 



