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geographical position and sea-climate“. It remains as a faet that the same species has different
sizes at different localities. Thus the spécimens of Philomedes globosa measured by me were
only 2,4—2,6 mm. at Skager Rack vvhile the same species attained a length of 2,9—3,1 mm.
at Greenland. This difference in length is not due to the species undergoing a different
number of moults before maturity under different external conditions. The number of larval
moults in the Cypridinid group seems to be constant for every species, as is showu above.
Corresponding classes of length were fotind at the different localities, but the absolute
measure-ments are different; cf. Philomedes globosa. This difference in length really seems often to
be accompanied by a difference in the growth-factor. Unfortunately my material was not
large enough to work out a definite answer to this problem by means of it. A faet that
supports, however, the idea that there is sometimes an alteration of the growth-factor is that
the embryos in the brood-chamber of large individuals are often not essentially larger than
those in small individuals. (In the large individuals, on the other hånd, the number of embryos
is often larger than in small individuals.)
The final result of my investigations is thus that the
growth-factor du ring the post-embryonal development of the
Ostracods is presumably an inherited factor, but it is rather
strongly influenced by exter nal circum stance s; in addition in
a number of species it is not quite the same du ring the whole
post-embryonal development. It thus seems as if Brooks’s law, as formulated
by G. H. Fowler, 1909, p. 224, needs a not inconsiderable modification. Before it is
re-formulated, however, it will be necessary to investigate a still larger material; moreover the
importance the abimdance of nourishment, temperature and other external conditions for the
rapidity of growth must first be studied.
In spite of this the law even as formulated at present seems to be very useful. G. H.
FOWLER himself has estimated it correctly when he says, 1909, p. 258: „On the other hånd,
I have little doubt that the law as phrased on p. 224 is a sufficiently accurate weapon for the
zoologist to use in combination with the morphological evidence, even if the words „fixe d
percentage“ may require revision at the hands of the niathematician“.
Summary of the
results of my
investigation of tilis
problem.
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