t>ft)ie Fishery Board for Scotland, 



gation, for it has been necessary not only to carry on the research, but in 

 the course of its progress to elaborate and control the methods by which 

 such an investigation should be pursued. The time and labour which 

 have been expended upon this tentative work have not been thrown 

 away, but have led to results which will be of the greatest value, although 

 at present these results may appear hardly commensurate to the labour. 

 But the material accumulated will be of much value for future work. 

 The methods to be employed have been thoroughly tested and simplified, 

 so as to be of easy application in the future. 



At the outset of the inquiry it was anticipated that a method would be 

 discovered by which the mycelial fungi could be readily separated from 

 the lower forms, such as torula, sarcina, and the various forms of bacteria, 

 and that thus either class could be separately investigated, without re- 

 gard to the others. This has not proved to be the case, except to a limited 

 extent. Every sample of water contains many forms of these lower 

 organisms, and it is necessary to isolate and study separately each indi- 

 vidual form, in order to arrive at accurate results. Many can be 

 separated with great facility, but others, owing to their slowness of 

 growth, or the requirement of special conditions for their development, 

 can only be isolated with greater difficulty. The methods by which this 

 result has been attained will be described later, as they may serve for a 

 guide to future observers. 



The investigation being in great measure a novel one, it has been one 

 great object to isolate and describe, as far as possible, all the organisms 

 which have been met with, so that they may be readily recognised in 

 future. And whilst a large number have been isolated and studied suffi- 

 ciently for future recognition, each species is being further subjected to 

 special investigation as to its reactions in various media, and under 

 different conditions of growth, &c. 



In the present report it is proposed to deal only with some of the bac- 

 teria and allied growths (sarcina, &c.), leaving the mycelial fungi for a 

 future report. These latter require for their exact recognition a more 

 exact study of the mode of fructification, &c., under various conditions ; 

 and whilst many of the commoner moulds of the classes Penicillium, As- 

 pergillus, and Mucor have been easily recognised, others have not yet been 

 identified. 



As a preliminary to all investigations of micro-organisms in water, it is 

 important to ascertain what is the number of bacteria or spores present 

 in a given volume of water. This is not only valuable as a guide to the 

 degree of dilution desirable for the further experiments, but it is also of 

 the greatest importance in relation to the purity of the water and its com- 

 parative freedom from decomposing organic matter. Bacteria are always 

 present in especially large numbers in those parts of rivers which are 

 near the inflow of sewage, and their abundance serves in some degree as a 

 test of the proportion of sewage contamination. A large amount of other 

 dead organic material also aff'ords a favourable nidus for their develop- 

 ment. And there can be little doubt that apart from the direct power of 

 producing disease, which is possessed by some forms, the presence of a 

 large number of those forms which have for their especial property the 

 production of decay and putrefaction of dead organic matter, is directly 

 prejudicial to all the higher forms of animal life. 



Bacteria can live on almost any dead organic material, and it is largely 

 through their agency, as above stated, that such matter is decomposed 

 and rendered available for further use. Moulds and allied genera, how- 

 ever, flourish most luxuriantly upon partially decayed matter or upon 

 specially prepared food, hence they are much more vigorous where 



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