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

DEVELOPMENT OF AMPHIBIAN KIDNEY 463
out the anterior prolongation. This condition persists to the
end of the first year after metamorphosis.
The condition during the second year (Text-fig. 3, D) has
been discussed above. The changes during the third year are
only those which are required to bring the second-year condition
to functional maturity.
The changes whereby the central strand, running caudad
through the testis from the anterior prolongation, acquires
TEXT-FIG. 3.
Diagram to show the origin and growth of the vasa eflerentia.
AP., anterior prolongation; DAP., degenerating anterior prolongation;
K., kidney; RVE., solid sheet of tissue from which both AP.
and VE. are produced; T., testis; VE., vasa efferentia.
connexions with the testis-tubules (' ampullae') has already been
adequately described by Witschi (loc. cit.) and confirmed by
Van Oordt (loc. cit.). The anterior prolongation itself (ap.
fig. 32, PL 23) rapidly degenerates. Several writers (Van Oordt,
Swingle) have reported disconnected lengths of tubule in the
fat-bodies of post-metamorphic frogs and there is evidently
considerable individual variation in the period at which degeneration
takes place.
The vasa efferentia themselves (fig. 30, PI. 23) do not alter in
their renal attachments, though the straight tubules (st., fig. 30,
PL 23) are now much bent by the attachment of excretory units.
It is interesting to note (fig. 16, PI. 22) that even during the
third year there is a close association between the point of entry
of the vasa efferentia and the point of exit of the renal veins.
NO. 311
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