New-York tribune., 1903-05-31

out Of any j1veniIe worker not yet liberated
from its cell it is only necessary to administer
special food. Darwin, indeed, thought that diet
had more % do with variation than any other
cause. DR. J. a. Allen Of the American Museum
of Natural History in this city, has remarked
that, in a general way birds and animals IN
North America increase IL size the more north
erly the latitude.
A change in some Of the important conditions
of life might conceivably lead to the acquisition
Of new characteristics by a species or race In
two ways If the altered environment operated
only to the same degree on each of q hundred
generations then the last should show no
greater departure from the original type than
the first or second. IT, however, each generation
not only experienced direct modification but also
passed along to the next one even the most
minute amount of newly acquired color, weight
or other characteristic. then there should be
gradual and increasing alteration in the species
until adjustment to the changed conditions was
fully effected The latter process is implied ID
the term cumulative" and Weismann concedes
this IN at least one instance He says OF two
va. ieties f the sane species of butterfly, one
found III Germany and the other in Italy, that
they may have originated from "a gradual
cumulative influence Of the climate, the slight
effects Of one summer or winter having been
transmitted and added to from generation to
generation" Seemingly, he gives away his case
against inheritances Of acquired characters by
the admission, although he goes on to offer d
particular explanation to make it fit his germ
pIasm7 doctrine So long as experts are not
agreed on this question of cause, therefore, the
Iaity are justified in believing that the variation
Of offspring from parents may be due to one or
mere Of several causes including q change Of
environment
Dr. Vernon does not hold that natural selec-
ton Is the only agency at work in the preser-
walton of some species and the extinction OF
others He does. however cite some recently
observed instances Of its operation Measure
ments Of the frontal breadth of crabs in Plym-
outh Sound England in 1893 1895 and 1898,
showed a rapid dimiaution in this one dimen-
sion III proportion to length. Professor Weldon
attributes the change to the recent accumula-
ton OF china clay IN the water. in conse-
qtlence Of the construction of a big breakwater
Formerly the clay. which came down from
Dartnloor streams went out to sea in the strong
currents of the sound In big crabs this ma
terial lodged in the eiIls while it did not get
into those Of smaller ones. The "httest' sur
viyed and their offspring is adapted 10 new con-
ditious After q very severe storm on the New
England coast 13G helpless sparrows were col
Iecl-d. or these scventy-tWo revived. and sixty
four died Upon measuring them carefully Pro
f-esor Bumpus found that the survivors were
closer TO the mean size than those which sue
cuubed to the elements. He con@iuded- Nat
lIraI selection Is most destructive Of those birds
which have departed furthest from the ideal
type and its activity raises the general standard
Of excellence by favoring those birds which aT-
proach the structural type