1851.) OF THE ROYAL INSTITUTION. 13 
in the centre of the egg: it then divides; and each division, attract- 
ing the vitelline matter of the egg about it, divides that matter into 
two parts. This division is repeated with the same result, until the 
principle has diffused itself by indefinite multiplication through the 
whole yelk which then constitutes the ‘ germ-mass.’ 
The next stage is the formation of the embryo: certain of the 
minute subdivisions, called ‘ nuclei’ or nucleated cells, combine and 
coalesce to constitute the tissues of the embryos: they are afterwards 
incapable of generating. If all be so metamorphosed the organism 
cannot procreate of itself; but if a part only of the germ-mass be 
metamorphosed into tissues, the unchanged remnant may, if nutri- 
tion, heat, and other stimuli are present, repeat the same actions as 
those that formed the first germ-mass, and lay the foundation of 
future embryos. 
In proportion to the amount of the substance of an organism 
which retains the primitive condition of cells, is the power of pro- 
ducing new individuals without receiving a fresh supply of the 
pollen-principle. 
Thus in a plant, when the seed has received the matter of the 
pollen-filament, analogous changes take place to those that have 
been described in the animal egg, and the embryo plant appears 
in the form of the cotyledonal leaf with its radicle or rootlet. 
From this shoots forth another leaf with its stem: and the cellular 
substance of the pith with its share of the pollen-principle goes on 
developing fresh leaves and leaf-stalks; until a provision for de- 
veloping fresh pollen is made by transforming certain individual 
leaves into a higher form of the ‘ phyton’ or elemental plant. Thus 
a generation or ‘whorl’ of leaves assumes the character of sepals, 
another that of petals, a third that of stamens, a fourth that of 
pistils: and in the two latter forms we recognize the analogues of 
the perfect male and female of the animal. 
The development of the compound polype follows very closely 
the stages of the compound plant, which we call shrub or tree: 
the ovum, like the seed, having received the pollen-principle, is 
converted into countless cells and nuclei of cells by the process for 
diffusing that principle through, or of assimilating it with, the matter 
of the egg. Then certain germ-cells are metamorphosed into a 
ciliated integument, and the larva starts forth in a state answering 
to the cotyledonal leaf of the plant: the ciliated larva settles, 
subsides, and shoots up a stem from which a digestive polype is 
developed, answering to the leaf: but the pollen-force not being 
exhausted, a second branch and polype are developed, and so on 
until a preparation is made for a fresh supply of pollen-force, by 
metamorphosing the polype into a higher form of individual; and 
this, in many compound pelypes, is set free in the shape of a 
minute medusa. 
