BACTERIOLOGICAL STUDY OF WATER. 503 



more exactness when counting colonies on a circnlar 

 plate. ^ 



Parks {Journ. Bad. and Path., 1896, vol. iv. No. 1) 

 has introduced a cheap and convenient modification of 

 Lafar's apparatus.^ It consists of a sheet of white 

 paper on which is printed a black disk that is ruled 



Fig. 101. 



Park's apparatus for counting colonies (reduced one-third). 



with white lines, in somewhat the same fashion as is 

 Lafar's counter, though the areas of the smallest sub- 

 divisions are not of one size and do not bear a constant 



1 Lafar's apparatus is to be obtained from F. Mollenkopf, 10 Tiiorstrasse, 

 Stuttgart, who holds the patent for it. Its price is about 8 or 9 marlis. 



2 Copies of this apparatus are to be had of Ash & Co., 42 Southwarli Street, 

 London, or of Lentz & Sons, North Eleventh Street, Philadelphia, Pa. (The 

 cost is but a few cents per copy.) 



