1040 SUMMARY OF CUEEENT EESEAECHES RELATING TO 



subject. Following the example of Bornet and Thuret in their 

 'Notes Algologiques,' the author publishes his observations on sepa- 

 rate species without awaiting the time when he will be enabled to 

 publish a more complete work. 



In the morphological part of his paper Prof. Reinhardt discusses 

 the development of a few Chlorophyceae, and enters into more details 

 with regard to some of the Cyanophyceae, and especially the Phseo- 

 sporeas (the conjugation of Ectocarpus siliculosus and the growth of 

 Sphacelaria). As to the Ehodophycese, only short remarks are given, 

 more particularly as to pores in their external covering. The chief 

 attention has been devoted to the Bacillariacese, and the paper con- 

 tains a good deal of new observations on the structure of gelatinous 

 colonies, the structure of the cell and its protoplasmic parts, and the 

 auxospores. The systematic parts will appear in a subsequent issue. 

 Movement and Formation of Mucilage by the Desmidiese.* — 

 Herr G. Klebs describes four kinds of movement in the desmids, viz. 

 (1) A forward motion on the surface, one end of the cell touching 

 the bottom, while the other end is more or less elevated, and oscillates 

 backwards and forwards during the movement ; this is especially well 

 seen in Closterium acerosum. (2) An elevation in a vertical direction 

 from the substratum, the free end making wide circular movements ; 

 well seen in Closterium didymotocum. (3) A similar motion followed 

 by a sinking of the free end, and an elevation of the other end, and 

 so on alternately, characteristic of Closterium moniliferum. (4) An 

 oblique elevation, so that both ends touch the bottom, lateral move- 

 ments in this position, then an elevation and circular motion of one 

 end, and a sinking again to an oblique or horizontal position, seen 

 best in strongly curved species of Closterium, as C. Dianse and 

 Archerianum. These movements are none of them peculiar to par- 

 ticular species ; several of them are often combined in one. A free 

 swimming on the surface was never observed. 



The two first of these kinds of movement depend on the formation, 

 during the motion, of a filament of mucilage by which the desmid is 

 attached to the bottom, and by the gradual lengthening of which, 

 from the formation of fresh mucilage, it rises. This filament is best 

 detected (e. g. in C. didymotocum') by tinging by a weak solution of 

 methyl-violet, which does not kill the desmid ; fuchsin also answers, 

 and cyanin, though not so well ; other pigments fail in staining it. 

 Many species of Euastrum^ Cosmarium, Pleurotaenium, and Staurastrum 

 exhibit the same phenomenon. The rapidity of the movement and of 

 the formation of the filament vary with the conditions and with the 

 species, many species exhibiting no trace of the former ; the most 

 rapid motion observed in C. acerosum was 112 /a in thirty seconds. It 

 is subject also to periodic variations, with alternations of complete 

 rest. The greatest length of filament measured was 3 mm. 



Light exercises an influence on the direction of the movement of 



desmids similar to that of zoospores ; but the power of motion itself 



appears to be very little affected by light. The elevation above the 



substratum appears to be independent of the direction of gravitation. 



* Biol. Ceutralbl, v. (1885) pp. 353-67. 



