

«FINAL DECISIVE EXPERIMENTS —_287 
_ Infecting Bacteria must be endowed also with 
mobility in order to be enabled to penetrate the 
cell wall which they have previously softened. 
The only other possibility, apart from hetero- 
genesis, of accounting for the appearance of the 
Bacteria within the closed cells would be the 
supposition that germs of micro-organisms have 
been “latent” within the cells. But of this no 
proof has ever been given. Bacteriologists fail to 
find evidence of their existence, and the verdict of 
science has, in fact, been adverse to this supposition. 
Let us now take another case and one in which 
the development of Bacteria from ultra-microscopic 
particles can be watched stage by stage. In Cyclops, 
a little water-flea, the abdominal appendages are 
furnished with a number of spines or sete, in the 
interior of which only structureless protoplasm is 
to be seen, free from granules. This protoplasm is 
so clear that it has a glass-like appearance. When 
one of these little creatures is placed in a drop of 
distilled water on a microscope slip, and a covering 
glass is applied, it soon dies. We may then examine 
some one of the larger spines from day to day. At 
the end of a couple of days, when the specimen is 
kept in a damp chamber and the weather is warm, 
instead of protoplasm free from all visible particles, 
such as originally existed, there is the first appearance 
of some minute motionless specks, which gradually 
increase in number and in size till some of them 
show themselves as motionless Bacilli. About the 
sixth day, some of these Bacilli begin to exhibit the 
first signs of movement, and soon we have a seeth- 
