312 The Development of Organisms l'^jomS^i^^ec?!'^^S^ 
tion complete dans les liquides qui la renferment, le microscope le 
plus perfectionn^ n'y demontre absolument rien." This, however, 
is the weak point of the hypothesis, which has that purely negative 
basis on which it is impossible to build with safety. Thus, it does 
not at all follow that the organic germs are absent simply because 
they cannot be discerned. It might as well be said that, before the 
invention of the microscope, infusoria themselves did not exist, since 
they were then invisible to the unassisted eye. The presence of a 
decomposing organic substance, however, shows clearly how these 
germs may exist in the infusion, although invisible, before the for- 
mation of the pellicule fvoligere. For although the substance 
itself may be so completely dissolved that it cannot be discovered, 
the particles of which it is composed must be present in the fluid, 
and if so, since there is nothing to show that they lose their organic 
character, why may not the germs of the future infusoria thus 
exist? In the infusions of vegetable pollen, well defined rings, 
which doubtless are examples of the organic jpellicule, make their 
appearance long after the development of the fungi and infusoria. 
The conclusion I have come to on this question, judging from 
the above experiments, is simply that the infusorial germs are 
identical with the particles of the decomposing substance of which 
the infusions are made. The monads and bacteria, whose cadavres 
make up the jpellimle j^roligere, are exactly the same, in every 
respect, apparently, as the monads and bacteria which exist in 
the seeds of plants, and which give rise to the infusoria subse- 
quently discovered in these seeds and in the water in which they 
are placed. Even the pollen-cell is full of the microzymas from 
which the monads and bacteria of the tissue are formed, and 
infusoria are no less abundant when the conditions necessary for 
their development are supplied. To the same category, without 
doubt, belong the so-called oil-globules of milk, which also, as we 
have seen, furnish numerous infusoria. The character of these 
globules is shown clearly by their relation to the corpuscles of the 
blood ; it having been proved that milk-globules, if injected into 
the arterial system, finally take the form and character of the 
blood-corpuscles, which may theoiselves probably undergo the same 
process of development as the former exhibit when infused. 
In these various facts we see a connection between the animal 
and vegetable kingdoms much more fundamental than has hitherto 
been supposed. The peculiar position occupied by infusorial germs 
in the tissue, the pollen, and the seeds of plants, shows that the 
latter are absolutely dependent on the former for their development, 
if not for their very existence ; and, in fact, it seems to me that 
whether the final result shall be animal or vegetable, depends 
wholly on the conditions under which such germs are brought to 
maturity. Their nature is probably alUed to that of the infusoria 
