Spectral Colours on the Sporulation of Saccliaromyces. 31 
through the glass door and the coloured screens and then played 
upon the surface of the cultures on the gypsum blocks. 
The screens acting as front windows of the tinned boxes 
were glass cells filled with various coloured liquids. In the case 
of red light in the series of experiments Nos. 1 and 2, there 
was a screen of red glass which passed the red and yellow rays, 
and in the later experiments the screen was of the same red 
glass with a water cell in front like that containing the green 
and blue solutions. The solution forming the green screen was 
a mixture of aqueous solutions of the dye known as Double 
Green (S.F.) and Naphtbol Green B [c] ; and the solution forming 
the blue screen was an aqueous solution of ammoniacal copper 
sulphate and crystal violet which cuts off all rays except the 
blue and violet. These three screens were spectroscopically 
examined, and they respectively transmitted the red, green and 
blue rays, so that the overlapping of the three completely oblite- 
rated the passage of light. In addition to the coloured screens, 
experiments were also conducted at the same time with ordinary 
light and in the dark. In the case of the former the screen 
contained merely distilled water ; and in the latter, the seeded 
gypsum blocks were enclosed in a closed wooden box and placed 
at the back of the incubator. The seeded gypsum blocks were 
then all placed in their respective positions in the different boxes, 
and they were allowed to incubate at 24 — 25°C. with the lig'n 
of the lamp placed in front of the glass door of the incubator. 
Experiments. 
In the first series of experiments pure cultures of Hansen’s 
S. Cerevisice I. and S. Ellipsoideus I. were seeded in very thin 
layers on the surfaces of the gypsum blocks, and they were 
examined from time to time. The following is a detailed account 
of the observations. 
14 February. 
6 p.m. The blocks were seeded and left to incubate. 
15 February. 
9.15 a.m. The cells were very granular in the two series but there 
was no appearance of spores. 
4.30 p.m. Red Liyht. The granules of some of the cells began to 
form sporulation rings. 
Green light. No attempt at sporulation. 
Blue light. No attempt at sporulation. 
White light. No attempt at sporulation. 
