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

466 PETER GRAY
It has been shown (Gray, 1930) that there arise throughout
the whole length of the kidney a series of early units which
degenerate throughout the length of the functional kidney,
except for a slightly later generation which persist as straight
tubules. The present investigation has shown that these straight
tubules are all that remain of the sexual kidney shown more
clearly in Triton. Now there is a marked similarity between
the development of the straight tubule units and the tubules
of the seminal vesicle. Each starts as a capsuloblast vesicle,
delayed both in its origin and development; each is primarily
devoted to a sexual function. It seems reasonable to suppose
that at one time the sexual units extended throughout the whole
length of the kidney and that they have been retained only at
the anterior and posterior ends, in which regions alone does
there exist any need for a sexually specialized unit.
The outstanding peculiarity in the development of the seminal
vesicles is their origin from separate blastema condensations
and not from the archinephric duct itself, which latter would
be the normal thing to have happened in the course of a separate
evolution.
E. REVIEW.
The facts brought forward in this paper do not justify a
lengthy comparative discussion. Nothing is known about the
post-metamorphic development of the kidney in any other
amphibian, and the few fragmentary papers which have appeared
on the later development of the kidneys in other groups offer no
opportunities for comparison. The formation of the vasa efferentia,
even though here fully described for the first time, shows
no departure from what is already known for other groups of
vertebrates. It has long been accepted that the testis-kidney
connexion in birds and mammals is primitive, and not a secondary
production of either organ.
The discussion of the development of the frog's kidney is
of more interest. It is now perfectly clear that the sexual
and asexual kidneys in Amphibia are distinct from each
other in origin and become intermingled only in course of
development.
The sexual kidney is represented by two sets of units, the