336 



Appendices to Fifth Annual Report 



describing also those of less frequent occurrence, to establish a sort of 

 chart for the guidance of future observers. 



It might be hoped also that we should be able to detect the presence 

 and prevalence of any special forms, either such as are directly connected 

 with disease, as Saprolegnia, or of allied forms which may nourish under 

 special conditions favourable to the development of pathogenic species. 



It is not easy to determine, by the method which we have adopted, the 

 relative prevalence of the several forms described. In the enumeration of 

 the points of growth upon the plate, it is only possible to apply very imperfect 

 methods for discriminating the various forms. If, for example, the water 

 under examination be diluted with four times its quantity of sterilised 

 distilled water, the number of points of growth appearing on the plate by 

 the third day may be only 100 or so. Of these a certain number will 

 have liquefied the jelly to some extent, and will be described as 'moist;' 

 others may show traces of colour or peculiarities of form of growth, which 

 may be further particularised. But even with such an enumeration, it is 

 extremely difficult to say subsequently how many points of any individual 

 species were present. 



We can only judge of this by meeting the same species frequently, or by 

 making a large number of highly-diluted cultivations, and allowing them 

 to grow for a longer time. This is impeded by the rapidly-spreading 

 liquefaction produced by some bacteria. 



We have, however, been able to aid this part of the investigation in 

 another way, viz., by studying very carefully the mode of growth of the 

 individual organisms in the plate at the early periods of their growth. 

 This is done by making fresh plate cultivations after isolation of the 

 species. These fresh plate cultivations are also essential, in order to 

 ensure thorough purity in the cultivation. 



We have not, as yet, since the isolation and study of the several 

 organisms described, made any further cultivations of river water, with a 

 view to the determination of the relative frequency of the several forms. 

 This we hope to do shortly. 



What we propose at present is to give such an account of those which 

 have been thoroughly studied up to the present as may aid in future 

 observations. 



We have not thought it necessary to describe the commonest species, 

 such as Bacillus subtilis, which are well known and easily recognised. 



Mode of Cultivation. — This has already been fully described in the 

 previous report. It is only necessary to add that, in the case of the 

 bacteria described, in nearly every case the cultivations were derived from 

 plate cultivations ; whilst in the case of the higher fungi they were more 

 frequently taken from the bread-paste flasks. As far as possible, every 

 point of growth upon a plate which presented any peculiarities was made 

 the source of a fresh inoculation of a tube. From the growths in these 

 tubes fresh plate cultivations were made, and this process repeated twice 

 or more, in order to secure absolute purity of the organism. Its growth 

 was then studied in bread-paste again and again, and in some cases in a 

 new kind of jelly devised by Mr Edington, made from Irish moss. 



Special Organisms Found. 



Amongst the various forms of micrococci present in the water, two are 

 of sufficient importance to be separately described. 



1. Magenta Micrococcus. — We had observed that in many of the flasks 

 a bright red colour was produced mixed with the growth of other fungi. 

 The colour was sometimes a deep lake, at others of a dull flesh tint. This 



