212 Biological Controversy and its Laws. [April, 
to be gradual, whilst in Mr. Mivart’s opinion it may be 
sudden. But are sudden changes of climate or other outward 
circumstances sudden ? As to the latent internal tendencies 
they seem to involve greater difficulties and a more frequent 
recurrence to miracle than the old hypothesis of special 
creation. 
But passing over these minor difficulties we come to the 
main question — the working of the hypothesis. We have 
before us certain phenomena, facets, and their relations. A 
new theory is placed in our hands : how far does it accom- 
modate itself to phenomena ? Can we show that it explains 
what we actually find, whilst if the faCts were different they 
would clash with the theory ? Does it give us any hints 
into what channel we are to direCt our observations ? 
Scarcely ; it lays before us two unknown powers, — the in- 
ternal tendencies and the complex of external influences, — 
and bids us from these deduce the animal kingdom. How 
are we to discover the magnitude, the direction, the modus 
operandi of either, much less mutual reactions ? Surely such 
a theory is too accommodating, and would lend itself as 
readily to the monsters of heraldry and the phantoms of 
mythology as to animals that ever have existed. 
Let us once more take Mr. Mivart at his own words, or 
rather at his own illustration. On the glass disc, then, lie 
the sound-figures traced in sand, resulting from the last 
application of the violin-bow. Let it be now applied in a 
different manner. Instantly, not one, not some, hut all of 
the figures are altered. Translating the symbol into the 
thing symbolised, this would mean that in a certain or- 
ganic species — say a butterfly — all the eggs deposited after 
the new external influences had come into play would yield 
inserts not slightly but abruptly modified, and the old form 
in a few weeks, or at most months, would entirely disappear. 
So far this would suit Mr. Mivart perfectly, dissenting as he 
does from the old maxim that Natura facit nihil per saltum, 
for which he would substitute “ facit multa ,” if not “omnia.” 
But how does it agree with fadts ? On this supposition the 
rise of a new species would always be attended by the ex- 
tinction of an old one. Never would a species branch out 
into two or more, nor would the old form survive the ap- 
pearance of the new, save in some region to which the 
modifying influences might not have extended. Thus on 
Mr. Mivart’s principle the multiplication of species, if it 
took place at all, would be exceedingly slow, and there could 
be no branching out into a number of closely approximating 
forms. 
