, 1876-07-29
sOuE NEW BOOKS.
oarwin's Theory OF pangene,i''
iFrom Tho Vow York sun.

NNI NhAANN ~ t'tN''N'' N''N '+'''
lral selection developed by Darwin In
his Origin of Specics' seem TO have
made good its claim to general rccogn''
lion. I. would BE- absurd to say that ii
nas attained a place beside the law OF
sruvitalion among the universally ap'
proved deductions of science, yet It's
,oo,hold is probably more secure than
hat of the nebular hypothesis, or OF the
.ndulatory theory OF light The doc
:rine Of natural selection, however, pre-
supposed variability as the constant char'
acter Of every organism. This p"sinia'e
rss been vehcmcntly impugned, and the
volumes before US, The Variation Of An
,nas and Plants under Domesticati0n
CAppletons,) may be said TO form a
oyramid of conycrginy and cumulative
Argtment pointing to the correctness OF
The assumption, The second edition OF
he work, which now appears alter
lapse of some seven years, has been but
.ressed with much additional material,
and the provisional hypothesis OF pan
Genesis framed TO coordinate and reduce
beneath one law all the phenomena OF
diversity IN growth has been remode'!ed
and signally re.enforced.
The several sub.laws which govern
variability may tie grouped under the ei
(ects of use and disuse, including changed
habits and acclimitization, arrested de-
yelopment, correlated variation, the CO.
hesion of houologous parts, compensa'
.ion Of growth, the liability to deviation
of multiple parts, the position Of buds
with respect to the axis OF the plant
and, lastly, analogous variability. These
different subjects $" graduate into one
another that their distinction is often Ar
bitrary, but it will be convenient to con-
,idcr them briefly in detail before stating
the hypothesis which aims to combine
the diverse modes Of Inherited mutabiiity
under q general law.
II is notorious that increased use or
action strengthens muscles, glands,
sense, organs, &C., and that disusc weak.
ems them. 1t has been experimentally
proved that the flow Of blood is greatly
augmented toward any part which is
performing work, and sinks again when
the part IS at rest. Consequently if the
exercises is frequent, the vessels expand
and the part is better nourished. When
Hunter inserted, for instance, the spur OF
cock into the comb, which is well sup.
Piled with blood vessels, il grew in one
case spirally To length of ak inches,
and in another case forward like horn,
so that the bird could not touch the
ground with it's beak. The rocking Of
the stem Of tree increases in = marked
manner the growth Of the woody tissue
in the parts which are strained. Every
one knows that hard work thickens the
epidermis on the hands, and when We
hear that with infants long before birth
the skin is thicke. on the palms and
soles, VIC are naturally led to attribute
this to the inherited effects l0f long.con-
tinued use or pressure. With respect TO
cattle, il 10 remarked tina, the lungs and
liver in the improved breeds, which take
little exercise and are supplied with nu'
tYitious and artificial food, "are consid-
erably reduced in size when compared
with those possessed by animals having
perfec. liberty" Again, our domessi'
Gated quadrupeds are all descended from
species with erect ears yet few kinds can
be named of which, At least, one breed
has not the ears dropping, With wild
animals, which constantly use this organ
.lihe a tunnel to catch every passing
sound, and especially to ascertain the
direction whence it comes, no race has
pendant ears except the elephant. Hence
the incapacity of erecting the ear is
plainly the result Of domesticatiop, and
has been reasonably ascribed by various
authors to the fact that creatures pro.
tected by man are not compelled babltu.
ally to use this organ, Col. Hamilton
Smith states that in ancient etIigies Of
the dog" with the exception OF one
Egyptian instance, no sculpture of the
earlier Grecisn era produces representa-.
sions Of hounds with completely droop-
ing ears; those with them half pendu-