166 NATURAL SGLENGE; Marcu, 
As in all the islands, there is a great difference between windward 
and leeward sides, the former affording some of the most beautiful 
scenery and luxuriant vegetation of any seen during the trip. 
KIDNEY TUBES IN AMPHIOXUS. 
Dr. THEopor Boveri, of Munich, has made one of the most 
striking zoological discoveries of recent times. In Spengel’s Zool. 
FYahrbiicher (vol. v., p. 429), he describes and figures a system of seg- 
mental canals in Amphioxus. These occur all along the region of the 
pharynx—one pair for each two pairs of gill-slits. They lead from the 
body-cavity to the atrial sac. There are go pairs altogether: the 
first and the last open by single ciliated funnels into the coelome ; 
the others by from five to seven funnels. A network of blood- 
vessels covers the funnels, and Boveri shows that carmine and indigo- 
carmine taken into the blood reach this network and are removed 
by the funnels. He gives a series of striking arguments in favour of 
regarding half the atrial cavity as the homologue of the primitive 
pronephric duct of Craniata. The whole paper is wonderfully con- 
vincing; and one has only to look for a moment at sections of 
Amphioxus to see the canals, and to be astonished that one has not 
seen them before. 
To readers who are not specialists in Zoology, the discovery of 
kidney tubes in Amphioxus may seem a matter of littlke moment; but 
the presence of a definite order and sequence in the development of 
the excretory organs is one of the strongest links binding together the 
Chordata—the group of animals which includes the vertebrates and a 
few lowly forms which have only the gelatinous rod which, in 
vertebrates, is the embryonic predecessor of the vertebral column. In 
all the members of this group, the excretory organs first appear as 
simple tubules, like the tubules of worms. These open at one end by 
a funnel into the body-cavity; at the other, into a longitudinal duct 
at each side. In higher vertebrates, like birds and mammals, a com- 
plicated series of changes supervenes, and the original excretory organ 
comes into use as part of the reproductive apparatus while the perma- 
nent kidney is developed in connection with the posterior end of the 
original organ. Probably there is no plainer instance of the embryo- 
logical law that the individual in its development travels along the 
path its ancestors traversed in their evolution; for practically every 
term in the series of changes in the higher vertebrates is preserved as 
the adult condition in some lower form. It was a puzzle why 
Amphioxus, which in so many of its organs preserves stages embryonic 
in higher animals, should be inexplicable in the set of organs most 
clearly identical-in other chordates; and now Boveri has shown 
that its excretory organs are precisely what analogy and homology 
alike demand. 
