Notes. 
373 
Similar results were yielded with saliva. 
To confirm this, an experiment was made exposing some extract to 
the light in a quartz cell, and simultaneously some of the same in 
a glass cell, keeping a third quantity in darkness. The results were : — 
D gave a reduction of *052, G one of *055, and Q one of -037 gm. Cu O. 
Q was retarded in the proportion of 52:37; G was accelerated in 
that of 55 : 52. 
The colouring matter of the barley-grain was by further experi- 
ments shown to have a certain power of protecting the diastase from 
the deleterious action of the violet rays, whether it was dissolved in the 
extracts used, or whether it was used separately as a screen placed 
before the cells in which the exposure to the electric arc was made. 
The screen in the latter case was contained in a quartz cell super- 
posed upon the quartz cell containing the extract. 
The results of the experiments so far point to the following 
conclusions : — 
1. Light, whether solar or electric, exercises a destructive effect 
upon diastase. 
2. The deleterious influence is confined to the rays of the violet 
end of the spectrum, the others being slightly favourable instead of 
destructive. 
3. The colouring matter of the barley-husk acts as a screen 
preserving the diastase from the destructive effect of light. 
The destructive influence continues after the exposure to light is 
discontinued, the exposed solution getting weaker and weaker till it 
had no diastatic property. The part of the solution kept in darkness 
maintained its diastatic power unimpaired for more than a month, by 
which time the exposed part, kept in darkness after its period of 
exposure, possessed no power to act upon starch. 
J. REYNOLDS GREEN, London. 
NUCLEOLI AND CENTROSOMES. — It may be of interest to 
state briefly here the results of some studies on these structures carried 
on during the past winter in Prof. Strasburger’s laboratory at Bonn. 
A somewhat fuller account, with a plate, has been published elsewhere k 
Although the occurrence of nucleolar substance in the cytoplasm 
has been observed by earlier writers, little significance has been 
1 Berichte der Deutschen bot. Gesellsch., Bd. XII, Heft 5, pp. 108-117. 
