sis has been frequently suggested. See my remarks in "Variationen
der Bluten", "Pringsheim's Jahrb. Wiss. Bot." 1905, page 298; also
Detto, "Biol. Centralbl." 1907, page 81, "Die Erklarbarkeit der
Ontogenese durch materielle Anlagen".), are to be included as such
potentialities in cells; the conception of specific structure includes
the WHOLE OF THE POTENTIALITIES OF A SPECIES; specific structure
comprises that which we must always assume without being able to explain
it.

A relatively simple substance, such as oxalate of lime, is known under
a great number of different crystalline forms belonging to different
systems (Compare Kohl's work on "Anatomisch-phys. Untersuchungen uber
Kalksalze", etc. Marburg, 1889.); these may occur as single crystals,
concretions or as concentric sphaerites. The power to assume this
variety of form is in some way inherent in the molecular structure,
though we cannot, even in this case, explain the necessary connection
between structure and crystalline form. These potentialities can only
become operative under the influence of external conditions; their
stimulation into activity depends on the degree of concentration of the
various solutions, on the nature of the particular calcium salt, on the
acid or alkaline reactions. Broadly speaking, the plant cell behaves in
a similar way. The manifestation of each form, which is inherent as a
potentiality in the specific structure, is ultimately to be referred to
external conditions.

An insight into this connection is, however, rendered exceedingly
difficult, often quite impossible, because the environment never
directly calls into action the potentialities. Its influence is exerted
on what we may call the inner world of the organism, the importance of
which increases with the degree of differentiation. The production of
form in every plant depends upon processes in the interior of the cells,
and the nature of these determines which among the possible characters
is to be brought to light. In no single case are we acquainted with the
internal process responsible for the production of a particular
form. All possible factors may play a part, such as osmotic pressure,
permeability of the protoplasm, the degree of concentration of the
various chemical substances, etc.; all these factors should be included
in the category of INTERNAL CONDITIONS. This inner world appears the
more hidden from our ken because it is always represented by a certain
definite