ment of the Kidney, and the Development of the - Journal of Cell ...

DEVELOPMENT OF AMPHIBIAN KIDNEY 447
(Gray, 1930), I was handicapped by a lack of material taken
between metamorphosis and sexual maturity in the fourth year.
The story which I then put forward is accurate so far as it goes, but
the three years following metamorphosis show great changes in
the posterior (non-sexual) portion of the kidney, more especially
with regard to the method of attachment of the units to the
archinephric duct.
The position in Rana is particularly complicated and differs
from Triton in that there is no clearly denned sexual region,
for the anterior portion of the male kidney has some excretory
function. The excretory and non-excretory regions grade into
each other. Each has its own special system for the connexion
of units to the archinephric duct. In the anterior, sexual region
the 'straight tubules' described in my previous research form
both the direct connexion between the vasa efferentia and the
archinephric duct and also serve for the attachment of such
excretory units as occur in this area. These straight tubules
also occur in the mid-region of the kidney, posteriorly to the
vasa efferentia, and there serve solely for the attachment of
excretory units. They are not, however, sufficient in number to
provide for the attachment of every unit, and large numbers of
secondary, arborizing, collecting-trunks arise from the blastema
which immediately surrounds the archinephric duct. During
the course of the second and third years after metamorphosis
the 'kidney' increases greatly in length, but this increase
is due solely to the addition of units to the
posterior region. No further transverse straight tubules
are formed, but these new units are taken up by numbers of
small collecting-trunks from the archinephric duct.
The fact that the kidney increases in length by additions to
its posterior region is well shown by an examination of the
relative position of the testis. Fig. 16, PI. 22, shows the appearance
of the urinogenital system of a 53-mm. Rana ternporaria,
taken and fixed in Bouin in July: that is, one which
would have reached sexual maturity in about nine months'
time. Even at this late stage the testis appears to lie relatively
farther towards the posterior end of the kidney than in the adult.
The posterior region of the kidney, moreover, is clearly differ-
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