are explained by Geometry. LY 
sphere. And the forms of development are either (1) discoid 
or membranous ; (2) axial or jilamentary ; (8) a combination 
of both, such as stellate; or if still kept in the massive state, 
then (4) granular, by the segmentation of a homogeneous- 
ness, whether spherule, membrane, or filament. 
Now, these deductions are so fully verified by all observa- 
tion, that I do not think it necessary to dwell upon this part 
of the subject. Thus a vegetative spherule, when placed in 
environments favourable to the deployment of its life, gives 
either a filamentary or a discoid frond, or one combining both. 
And when it has become full sized according to the hereditary 
type of the species, and the conditions of existence, conse- 
quently, are no longer favourable to the further deployment of 
life, then spherical forms are developed in it again which also ~ 
tend to divide by segmentation into smaller grains, often in a 
very beautiful and geometrical manner (in algee, pollen, d&c.), 
whereby the spore is reproduced and the species preserved. » 
Seeds also, and the same is true of buds and tubers when the 
conditions of the ambient media become favourable, develop 
into plants which are wholly composed of parts that are either 
discoid or linear, or of the nature of leaf and stem. Nor is 
it in the vegetable kingdom only that we find this law verified. 
The inner fabric of animals is entirely composed either of 
membranes or of fibres. And even as to their external forms, 
very many of them are discoid or radiant, and very many of 
them are linear. But here, it may be remarked in reference 
to the entire forms of animals, that geometrical properties of a 
higher order prescribe limits to the granting to them of simple 
and elementary forms. And, moreover, since even the simplest 
plant or animal consists of parts and particles, each of which 
has attained a perfected or matured form for itself, it is alto- 
gether necessary to determine the latter, before attempting to 
explain the forms of entire organised beings. 
Forms of Maturity. 
In the preceding investigation we have assumed that the con- 
dition of existence, at least in so far as the ambient medium 
is concerned, is either wholly unfavourable or wholly favour- 
able to the deployment of life; and the only change that we 
