vessel with the subintestinal vein), H renal vessel.

FIGURE 2.218. Transverse section of a primitive fish embryo
(Selachii-embryo, from Boveri.). To the left pronephridia (B), the
right primitive kidneys (A). The dotted lines on the right indicate
the later opening of the primitive kidney canals (A) into the prorenal
duct (C). D body-cavity, E visceral cavity, F subintestinal vein, G
aorta, H renal vessel.)

If we sum up the results of our anatomic study of the Amphioxus, and
compare them with the familiar organisation of man, we shall find an
immense distance between the two. As a fact, the highest summit of the
vertebrate organisation which man represents is in every respect so
far above the lowest stage, at which the lancelet remains, that one
would at first scarcely believe it possible to class both animals in
the same division of the animal kingdom. Nevertheless, this
classification is indisputably just. Man is only a more advanced stage
of the vertebral type that we find unmistakably in the Amphioxus in
its characteristic features. We need only recall the picture of the
ideal Primitive Vertebrate given in a former chapter, and compare it
with the lower stages of human embryonic development, to convince
ourselves of our close relationship to the lancelet. (Cf. Chapter
1.11.)

It is true that the Amphioxus is far below all other living
vertebrates. It is true that it has no separate head, no developed
brain or skull, the characteristic feature of the other vertebrates.
It is (probably as a result of degeneration) without the auscultory
organ and the centralised heart that all the others have; and it has
no fully-formed kidneys. Every single organ in it is simpler and less