of the Fishery Board for Scotland. 



181 



but mixed with some others. If, now, as soon as these distinct growths 

 can be recognised, a minute quantity is transferred from one of 

 them to a fresh flask containing bread paste, a fresh cultivation may be 

 obtained, in which one particular species preponderates,, and by successive 

 selections from cultivations some forms may be obtained nearly pure. 



But having thus partially separated the several species into groups, it is 

 necessary, in order to ensure absolute purity, to make fresh cultivations by 

 the gelatine plate method, by which the two or three species present may 

 now be more readily isolated. 



An additional advantage of the bread paste method which must be 

 emphasised, is the striking and characteristic appearances which many 

 bacteria and other low fungi present as to colour and form when culti- 

 vated upon such a medium (as bread paste), an advantage possessed also 

 in some degree by agar-agar jelly, and by potatoes, but far less readily and 

 continuously applicable in the case of these media. 



At the commencement of the investigation the mode of procedure is as 

 follows : — 



A long, thick sterilised platiuum needle is dipped into the water to be 

 examined, care being taken not to allow it to come into contact with the 

 neck or lip of the bottle, the plug is then removed from the bread paste 

 flask, and the minute droplet of water which collects at the point of the 

 needle is allowed to come in contact with the bread paste, the flask being 

 kept horizontal. The wire is then removed and the plug replaced. 

 Several flasks are inoculated in the same manner in order to obtain as 

 many varieties as possible. In flasks so inoculated various growths 

 soou make their appearance. The mould fungi were very numerous, 

 various species of Penicillia, Aspergilli, Mucors, &c., being found in 

 considerable numbers. The determination of the species of these funsji 

 is a matter of very great difflculty ; a lengthened observation of their 

 modes of growth, methods of fructification, &c., being necessary to do 

 this at all accurately. Numerous forms have been separated and 

 partially examined, but they have been set aside for future observation, 

 as the species of Bacteria were so numerous and required so much of the 

 time and attention that it was found impossible to include the fungi in 

 the present report. 



Bacteria. — Some of these made their appearance as naked eye growths 

 in about three days, others took much longer, even as much as ten days, 

 before they could be distinguished as definite growths on bread paste. 

 In all cases it was found necessary to take cultivations from each growth 

 as it made its appearance, for it was observed that some species, after 

 once getting fairly under weigh, grew so rapidly as to supersede all other 

 species in the flask, and it was not always the case that the one first seen 

 was the species that eventually retained its ground. 



By careful selection moderately pure cultivations may be obtained from 

 these flasks. In fact, for microscopic purposes, these are all that are 

 necessary, as where fairly successful cultivations are obtained, the typical 

 form so far predominates that it can be readily distinguished from any 

 impurities, such being present in much smaller numbers. For secondary 

 bread paste cultivations, too, these are sufficiently pure, if it be borne 

 in mind that the growth should be examined as soon, as it makes 

 its appearance. If it then corresponds in appearance with the part from 

 which it was taken, we may conclude that a description of the naked eye 

 characters of such a growth will serve all practical purposes. This 

 method, however, is not alone sufticient, and wherever possible it is 

 better to have the various forms perfectly isolated ; for this purpose the 

 gelatine plate method must be employed. This was subsequently done. 



