ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
671 
much higher than have commonly been employed successfully for such 
observations. Prof. Ward begins with an account of his bacteriological 
cultures, and gives in tabular form the characters of the species. He 
next discusses its classification, and remarks that many bacteriologists 
are not always sufficiently careful to look up the synonyms of the forms 
they describe, though this precaution is really more necessary in the 
deplorable state of their literature than probably in any other depart- 
ment of biology. The germination of spores is next considered, and 
the formation of stresses is described. The development of the spores 
is fully discussed, and is followed by measurements of the growth of 
the rods and filaments. Growth and cell-division come next under 
discussion. After some comparative measurements, the results of 
germination and growth behind glass screens are described. It is clear 
that growth occurs with increasing rapidity in suitable food-materials 
and under suitable conditions. The rate of growth may vary according 
to the action of certain factors partly external and partly internal, and 
this variation may be local in a filament, or general. Prof. Ward’s 
experiments show that the growth is slower on exposure to sunlight 
passing through certain screens, whereas it is not retarded perceptibly 
in light through other screens. It is possible that actively growing 
filaments may have some power of overcoming the detrimental action of 
rays which seriously injure or even kill the spores in a state of rest. 
There can be no question that exposure to direct sunlight kills both 
spores and filaments. Prof. Ward has made a series of very important 
experiments on temperatures, as he was by no means satisfied with some 
of the results that he obtained. So far as the spores exposed in the ripe 
resting condition are concerned, it may be regarded as proved that the 
blue-violet rays can retard or kill them apart from any temperature effect. 
Actively growing bacilli are affected by the light action which retards 
their growth and even eventually kills them. 
In attempting to trace the effects of light, it is so difficult to keep 
two growing filaments exactly at the same temperature under different 
conditions of illumination, that the quantitative results cannot be insisted 
on too much in detail, for there is always the suspicion that even a 
difference of less than one degree of temperature may affect the rate of 
growth. Some results suggest the possibility that the organism may 
even make use of rays at the red end of the spectrum in combating any 
effect of those at the blue end. Experiments made without the use of 
glass show distinctly that the spores are retarded or killed by five or six 
hours’ exposure to daylight even of low intensity ; and apart from tem- 
perature the growing filaments are often not measurably retarded within 
the period observed, but the evidence goes to show that the light slowly 
retards the growth. Whatever the light action consists in, it is evidently 
exerted by the more refrangible rays, and is the more pronounced, the 
more intense the light. It would appear that there are three points to 
be considered as regards the growth and behaviour of the organism : — 
(1) The rate of germination ; (2) the rapidity of post- germinal growth ; 
and (3) the time occupied in completing the life-cycle from spore to 
spore. It is impossible for us, with our space, to give a full account of 
the enormous amount of work which Prof. Ward has done on this 
bacterium. He is led by his studies to suggest that it might be worth 
