It seems difficult to conceive that this can be so; but we see that it _is_ so." ...

"For this property there is no fit term.
If we accept the word polarity as a name for the force by which inorganic units are aggregated into a form peculiar to them, we may apply this word to the analogous force displayed by organic limits." Dr.Jeffries Wyman,[196] in his paper on the "Symmetry and Homology of Limbs," has a distinct chapter on the "Analogy between Symmetry and Polarity," illustrating it by the effects of magnets on "particles in a polar condition." Mr.J.J.Murphy, after noticing[197] the power which crystals have to repair injuries inflicted on them and the modifications they undergo through the influence of the medium in which they may be formed, goes on to say:[198] "It needs no proof that in the case of spheres and crystals the forms and the structures are the effect, and not the cause, of the formative principles.

Attraction, whether gravitative or capillary, produces the spherical form; the spherical form does not produce attraction.

And crystalline polarities produce crystalline structure and form; crystalline structure and form do not produce crystalline polarities.
The same is not quite so evident of organic forms, but it is equally true of them also." ...

"It is not conceivable that the microscope should reveal peculiarities of structure corresponding to peculiarities of habitual tendency in the embryo, which at its first formation has no structure whatever;"[199] and he adds that "there is something quite inscrutable and mysterious" in the formation of a new individual from the germinal {186} matter of the embryo.