BACTERIOLOGICAL STUDY OF WATER. 503 



more exactness wheu counting colonies on a circular 

 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 niled 



Fig, lOL 



op ^ 



Park's apparatus for coanting 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 Lafer's apparatus is to be obtained from F. Mollenkopf, 10 Thorstrasse, 

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



- Copies of this apparatus are to be had of Ash &. Co., 42 Southwark Street, 

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

 cost is but a few cents per copy.) 



