308 



Profs. Percy Frankland and Marshall Ward. 



and exposures to sunlight passing through coloured glasses confirm 

 this result; but the observations are being continued in the hope of 

 getting a perfectly sharp record of the effects of each set of rays. 



The following series of experiments are quoted in detail, because 

 they teach several details of importance, in addition to proving the 

 main fact. 



On December 7 three gelatine plates and five agar plates were 

 prepared with spores from a very vigorous and virulent agar tube of 

 anthrax. The spores, which were quite mature, were not subjected 

 to heat, but simply shaken in sterile water to wash and separate them 

 thoroughly. 



The three gelatine plates were made at 35° C, the agar plates at 

 60° C, neither of which temperatures could injure the ripe spores. 



The three gelatine plates were labelled pi, p 2, and p 3, and the 

 agar plates p 4 to p 8 in order. 



Immediately after making the plates, all were exposed to the 

 December sun, except plates p 4, p 5, and p 6, and this was done as 

 follows : — In each case the plate had a stencil plate with a cut-out 

 letter on its lower face, and arranged as described above (p. 304). 



pi, a, gelatine plate with a large letter M, was exposed, face down, 

 to the light reflected from a mirror (see fig. 1) for three hours on 

 December 7, and for four hours on December 8, the interval being 

 passed in a cold room (t about 8 — 9° C), and then incubated at 20° 

 in the dark. 



p8 was treated in exactly the same manner. But this was an 

 agar plate with a large W. 



p 2, a gelatine plate with a large H, was exposed and treated in the 

 same way, except that no mirror was used, the latter being upwards 

 towards the sun. 



p 3, a gelatine plate with a large B, was similarly exposed, face up, 

 but a plane mirror arranged to reflect light down upon it. 



p 7, an agar plate with a large E, was treated exactly as the last. 



There now remain the three agar plates, p 4, p 5, and p 6, to 

 account for. 



p4 was placed forthwith in the dark incubator at 20° C. 



p 5 and p 6 were kept for eighteen hours in a drawer, the average 

 temperature of which is almost 16° C, and were not exposed till next 

 dav (December 8), when they lay for five hours, face upwards, and 

 with a mirror above them, p 5 had a small E, and p6 a broad but 

 small I, to let the light in. 



After exposure, these also were put in the same incubator with the 

 others. 



Nothing was visible to the unaided eye on these plates (except p 4) 

 until the 11th instant, though the microscope showed that germina- 

 tion was proceeding on the 10th. The plate p4<, however, had a 



