224 Transactions of the Society. 



added and the slip transferred to a moist cell containing a paper 

 ring, and incubated as before. 



Considerable eye fatigue is avoided and the organisms them- 

 selves protected by passing the light through a filter of Crook's 

 glass, vi^hich cuts off a large proportion of the ultra-violet rays. 



The advantages of this method are that the element of chance 

 in the successful carrying out of the manipulation is completely 

 eliminated. No special skill or practice is called for, no special 

 preparation is needed ; and the whole procedure can be carried out 

 without notice with the ordinary apparatus found on a bacterio- 

 logical laboratory bench; the time required is only one or two 

 hours. 



