PEDIGREE OF MONERA. 41 
origin of the whole tribe during the course of enormous 
periods of time. 
Upon the ground of embryological records, therefore, we 
can with full assurance maintain that all many-celled, as 
well as single-celled, organisms are originally descended from 
simple cells; connected with this, of course, is the conclusion 
that the most ancient root of the animal and vegetable 
kingdom was common to both. For the different primzeval 
“original cells ” out of which the few different main groups 
or tribes have developed, only acquired their differences 
after a time, and were descended from a common “ primzeval 
cell.” But where did those few “original cells,” or the one 
primeval cell, come from? For the answer to this funda- 
mental genealogical question we must return to the theory 
of plastids and the hypothesis of spontaneous generaticn 
which we have already discussed (vol. i. p. 327). 
As was then shown, we cannot imagine cells to have arisen 
by spontaneous generation, but only Monera, those primeeval 
creatures of the simplest kind conceivable, like the still 
living Protamcebe, Protomyxe, ete. (vol. 1. p. 186, Fig. 1). 
only such corpuscules of mucus without component parts— 
whose whole albuminous body is as homogeneous in itself as 
an inorganic crystal, but which nevertheless fulfils the two 
organic fundamental functions of nutrition and propagation 
—could have directly arisen out of inorganic matter by auto- 
geny at the beginning (we may suppose) of the Laurentian 
period. While some Monera remained at the original simple 
stage of formation, others gradually developed into cells by 
the inner kernel of the albuminous mass becoming separated 
from the external cell-substance. In others, by differentiation 
of the outermost layer of the cell-substance, an external 
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