ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 215 



Thallophyta. 



Algae. 

 (By Mrs. E. S. Gepp.) 



TJlva latissima in relation to Sewage-pollution of Sea-water.* 

 E. A. Letts and W. E. Adeney, in their report upon the pollution of 

 estuaries and tidal waters, treat of the nuisances caused by the growth in 

 large quantities and subsequent decay of certain green seaweeds, chiefly 

 TJlva latissima, with Enteromorpha compressa and E. intestinalis in less 

 quantity. For example, in Belfast Lough, Dublin Harbour, and 

 Southampton Water, the TJlva driven ashore by strong winds forms 

 banks which, rapidly putrefying in warm weather, emit an overpowering- 

 stench of sulphuretted hydrogen, often mistaken for a nuisance caused 

 directly by sewage. By appropriate experiments the authors determined 

 that when the TJlva ferments it is attacked by a form of bacillus which 

 probably acts upon the albuminoids of the alga, and certainly leads to 

 the production of propionic and other fatty acids, with carbonic anhydride 

 and hydrogen. Subsequently the TJlva is attacked by another form 

 of bacterium which leads to the production of ferrous sulphide and 

 sulphuretted hydrogen, such sulphur compounds being derived from the 

 sulphates of the sea- water or of the alga (and not from its albuminoids). 

 Further, the evidence shows that the occurrence of TJlva in quantity in a 

 given locality is associated with the pollution of the sea-water by sewage. 



A remarkable point is the high proportion of nitrogen in the chemical 

 composition of the TJlva, and also the avidity with which the alga 

 absorbs inorganic compounds of nitrogen, such as ammonia and nitrates 

 from sea-water. These properties suggest the employment of TJlva 

 latissima as a valuable source of ammonia. Enormous quantities of the 

 plant are washed ashore in Belfast, and, though the farmers cart it 

 away and put it on the land, they thus use but a very small fraction of 

 it. TJlva and Enteromorpha play a great part in nature as scavengers 

 and purifiers of polluted estuaries ; on the one hand they rapidly absorb 

 ammonia, nitrates and carbonic anhydride, the products of bacterial 

 action upon sewage ; and on the other hand they evolve quantities 

 of oxygen which, dissolving in the water and oxidising organic 

 matters, contribute to the purification of the sea and render it habitable 

 by marine animals. Experimental proof of these statements is afforded, 

 and coloured figures of the alga? cited are given. 



Method of Analysing Plankton.f — L. Mangin describes a method 

 of analysing the vegetable organisms of plankton, chiefly diatoms and 

 Peridinieas, these two differing profoundly in the nature of their 

 membrane. The membrane of the Peridinieas is of almost pure 

 cellulose, while that of the diatoms has its organic part composed of 

 pectic materials. For revealing the most minute structure of the 

 cellulose wall of the Peridinieae the best stains to use are the acid stains, 

 while for pectic compounds the basic stains are best. By these methods 



* Royal Commission of Sewage Disposal, Appendix vi. (1908) pp. 141-68 (pi.), 

 t Bull. Soc. Bot. France, lv. (1908) pp. 574-8. 



