ON THE DEVELOPMENT OF VEGETABLE ORGANISATION. 267 
ultimate molecules, or atoms of mineral or inorganic matter, and the 
simplest forms of animal and vegetable existence, we cannot doubt; but 
as we are incapable with the aid of the instruments which we at’present 
possess of tracing out and examining these elementary bodies, either in 
the one case or the other, we must be content to take our departure in 
this investigation from that part of the scale of progressive development 
of which our means of research, aided by our reflecting powers, permit 
us to acquire a knowledge. 
The ultimate particles or molecules of all mineral bodies have been 
conceived to be of a shape either perfectly spherical, or more or less 
inclining to a sphere, and these spheres or spheroids of most incon¬ 
ceivable minuteness, varying however in their size in bodies of a differ¬ 
ent nature, and probably also in their polarities or modes of attraction. 
In the simplest forms of vegetable or animal existence with which we 
are acquainted, the externa) configuration of the organic particles is the 
same as, or at least very similar to, that conceived to belong to the 
mineral molecules, namely, spherical or spheroidal. But there is this 
essential difference : the phenomena of the mineral molecules are best 
explained upon the supposition that they are homogeneous, or of like 
nature throughout, whereas, as far as our researches go, the ultimate 
forms of organisation are not homogeneous, but consist of a membran¬ 
ous or filmy envelope of extreme tenuity, inclosing within its cavity a 
transparent fluid, constituting in fact a close spheroidal cell or vesicle. 
It is not necessary for our present purpose to attempt to define the 
difference between the simple monads of animal and the simple vesicles 
of vegetable existence; and when it is stated that of the former five 
hundred millions have been crowded into the space of one cubic inch 
without apparently interfering with each other, and that of the latter 
still greater numbers have been observed to occupy the same space, it 
will be seen that the very minuteness of these bodies in itself opposes 
a barrier to our investigations, the bounds of which we cannot pass. 
The subject which more immediately demands our attention is the 
gradual development of the mysterious principle of life, as shown in 
the variations of organic structure throughout the scale of vegetable 
being, commencing with the most simple vesicle or germ of vegetable 
existence, and tracing the increasing development of the vegetable 
structure till we arrive at the most complex and elaborate of its forms. 
The most simple forms of vegetable existence, according to the views 
here expressed, of which we can form a conception is a close cell or 
vesicle, a simple vesicle consisting of a membranous film of extreme 
tenuity, enveloping and enclosing within its central cavity some fluid, 
or perhaps aeriform matter. Such a vesicle may be observed in the 
