of the Amazon Valley. 451 
ville (Cat. Ins. Coléop, recueillis par Osculati, p. 27), found in 
Keuador, probably on the banks of the Napo, is a further modi- 
fication of the A. Onca, in the direction of our var. Olivencius. 
There is also an undescribed species found at Cayenne (A, multi- 
guttatus, Laferté, MS.)*, which diverges from A. Onca in another 
direction; and this may with great probability be referred to the 
same type. It is the custom of naturalists, when they subordi- 
nate varieties to a species, to fix upon one of the forms as the 
original, to which the rest are referred : this original is generally 
the one first described or best known. In accordance with this 
usage, I have said that such and such forms are varieties of A. 
Onca ; but, strictly speaking, no form can be said to be a variety 
of another existing form unless it can be proved or shown to be 
highly probable that the one descended from the other, this other 
itself remaining meanwhile unchanged. It is necessary, there- 
fore, to guard against the error of supposing that the arbitrarily 
chosen forms we see placed as species, with varieties subordinated 
to them are the true parents of those varieties; for whilst the 
varieties were being formed the parents themselves may have 
been undergoing modification, and therefore the so-called species 
and their varieties may be all equally varieties of some common 
possibly extinct form. In the present case, all that I mean to 
convey is, that, reasoning upon the fact of much local modifica- 
tion in A, Onea, we are constrained to infer that other closely 
allied forms have been derived from a pre-existing one nearly 
resembling them; and this might have been either A. Onca or 
the common parent of A. Onca and its subordinatest. 
* T regret being unable, not having a specimen at command, to give a 
description of this species. 
t Some entomologists, however, believe that a local variety is an original 
creation equally with a species. Dr. Schaum, an author of high reputation, 
says, in discussing a case of local variation similar to the present one (Ber- 
liner entom. Zeitschr. 1861, p. 398), that many pairs of a species were 
originally created, and that, as there would be original differences amongst 
the individuals according to locality, so we have, at present, local varieties. 
This view will recommend itself to some minds by its extreme simplicity ; 
for the excessive complexity of the relationships between existing varieties 
and species, on the other view above stated, repels by its difficulty of 
unravelment, In no case does the remark of Bacon so well apply, to the 
effect that the subtlety of nature far exceeds the subtlety of man’s intellect. 
But Dr. Schaum’s view ignores the fact that many local varieties shade off 
into mere individual variations or differences, such as we see occurring 
amongst the offspring of the same parents, making it extremely probable 
that local varieties or races have been derived by ordinary generation, with 
modification, from pre-existing forms. The hypothesis of the persistence, 
under the same conditions, of a local variety from the time of its creation 
is also quite at variance with the great mass of evidence, supplied by 
geology, of great migration and dislocation of species during the glacial 
and other epochs. 
