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Appendices to Fifth Annual Report 



sary to conclude that the presence of a large number of organisms in 

 water is evidence of the special prevalence of bacteria. For the mode of in- 

 vestigation which has already been detailed (see p. 178 of previous Eeport), 

 determines only the number of fungoid spores and bacteria taken together. 

 Nearly all the lower fungi which we have isolated are capable of 

 growth upon the nutrient jelly employed. The method shows the pre- 

 valence of lowly fungoid life in water, and therefore indicates a favourable 

 condition for the propagation of all or most of such organisms, including 

 the Saprolegnia. It must, however, be stated that the bacteria in most 

 cases grow more rapidly, and some of them cause liquefaction of the jelly 

 before the appearance of most other kinds of fungi. Most of the higher 

 fungi which we studied were obtained in the first instance from cultivations 

 in bread-paste flasks. 



It has been one of our objects to endeavour to determine separately the 

 number of bacteria (Schizomycetes) and that of the higher orders (Blasto- 

 mycetes, Myxomycetes, Hyphomycetes). This can only be done by using 

 nutrient media which are incapable of supporting the life of one or other 

 class. Hitherto, no media have been found which will thus serve to 

 separate bacteria from higher forms, but we are not without hope that the 

 careful study of the life conditions of the many forms observed may aid to 

 solve the problem. 



The enumerations which have been made of water from the Tweed and 

 Dee respectively are of importance so far as they go. But in order to 

 attain any result of high value, it will be absolutely essential to establish 

 stations of observation at or near the rivers to be examined, and to make 

 continuous observations at various times of the day, conditions of rainfall, 

 temperature, &c. The work can only be done by a skilled observer, and 

 requires the expenditure of a large amount of time and patient laborious 

 observation. 



The difficulties attending any accurate enumeration are mainly due to 

 the fact that bacteria multiply with great rapidity in the water. Hence, 

 in a sample of water, which is carefully collected and secured in a bottle, 

 the number may have doubled in a very short space of time. The 

 rapidity of growth can be partly controlled by keeping the water at a 

 low temperature, and the comparative results can be checked by making 

 the plate cultivations at a uniform interval of time after collection. But 

 these checks are also liable to two sources of fallacy, one being that the 

 rate of self-multiplication is not the same for all forms of bacteria, the 

 other that some will grow readily at a much lower temperature than others. 

 Hence it is only in winter, or when the water is artificially kept at a tem- 

 perature near freezing-point, that the results are to be relied upon. If 

 the plate cultivations could be made on the spot, and then conveyed to the 

 Laboratory, the difficulty would be overcome. But in practice there is the 

 greatest difficulty in transporting them in such a way as to avoid entrance 

 of bacteria during transit, apart from the difficulties in making the cultiva- 

 tion. 



This source of error was, however, to a great extent avoided by the follow- 

 ing plan. The method, in its general features, has already been described 

 (see p. 178 of Report for 1885). The tubes were inoculated with a 

 definite number of drops of water measured by a graduated pipette, the 

 weight of each drop having been previously accurately estimated. The 

 jelly was not liquefied, but the drops were allowed to remain upon its sur- 

 face, and the tubes kept upright during transit. On arrival at the 

 Laboratory, the plates having been prepared, the jelly was gently warmed 

 until it was fluid, and then the tube slowly turned round and round until 

 the water containing the organism was thoroughly mixed with the jelly. 



