1875.] The Question of Organic Evolution. 193 
from the air, fitted up by a Deus quidam deceptor, with Mr. 
Gosse’s éuparoc? ‘The individual animal is evolved according 
to unvarying law from antecedent animals, at first as a 
simple and rudimentary cell, but gradually becoming differ- 
entiated and individuated as a complex and separate being. 
Does not analogy. indicate that such, too, must have been 
the origin of the groups we call species? Astronomy, 
physics, chemistry, can dispense with miracle; zoology and 
botany must prepare to do the same if they are to be recog- 
nised ‘as sciences at all. 
Turning from general considerations to individual cases, 
let us take the following evidence :—‘“ In the whole series 
of strata,” says Hilgendorf, ‘‘ the varieties of planorbis mul- 
tiformes are distributed in such a manner that individual 
layers are characterised as successive strata, by the exclu- 
sive recurrence or by the predominance of single or several 
varieties, which, within the layer, remain constant, or 
slightly variable, but towards the limits of the next layer, 
lead by transitions towards the succeeding forms. The in- 
termediate layers furnish evidence that the other forms 
originated by gradual metamorphosis from the earlier ones; 
they, moreover, render it possible to range form to form, and 
to trace the evolution backwards; hence it becomes mani- 
fest that, what above seemed distinctly divided meets below.” 
** The forms diverge so greatly,” adds Professor Schmidt in 
comment, ‘‘and are so constant in the main zones, which 
tell of periods of repose, that in accordance with old con- 
chological practice, they would be unreservedly claimed as 
species 7f the connecting links were not too conspicuous.” 
Finding such connecting-links—such plain evidence of 
continuous evolution in case of animals which, like the 
shell-bearing mollusca, have a characteristic portion of their 
structure composed of somewhat permanent materials—is it 
too much if we infer that, were the stone record undamaged, 
and were all animals equally imperishable, a like continuity 
would meet us in every group ? 
Turning to species still existent :—‘‘ Who that has read 
the comprehensive investigations of H. Miiller can doubt 
that the honey-bee, as it gradually attained its bodily advan- 
tages and peculiarities, developed likewise the higher mental 
powers, corresponding with the more minute and complex 
organism of her brain ?”? Or, again, look at the Ancon sheep 
—a mere variety, commonly so called by those who refuse to 
see that between species and variety no valid line of separa- 
tion can be drawn. Yet had this mere variety been placed 
in sole occupation of some country where it might have 
