854 
GEORGE C. PRICE 
certain that the bunch of tubules just mentioned arose from the 
branching of such an isolated cubule. Tn another case there was a 
short but complete break about the middle, so that for five sec- 
tions there was no trace of any part of the organ. Other examples 
of the same nature might be given. 
In the great majority of cases there is no connection whatever 
between the head kidney and the functional kidney. There is a 
short but complete break between the posterior end of the one and 
the anterior end of the other. In one case no break could be ob- 
served, and it was thought the two must be in some way connected, 
but upon sectioning it was found they simply overlapped, and 
that there was no actual union. In another case, however, che 
cavity containing the glomerulus of tne head kidney was joined 
to the duct of the functional kidney by a tubule, and also to the 
duct of the head kidney. In no instance was the duct of the head 
kidney connected with the duct of the functional kidney even by 
a rudimenc. But it would not be surprising if such a case should 
be found, since we know that the two are parts of one and the same 
duct in the embryo, and that they become separated by the degen- 
eration of a small portion of this duct. When only the adults 
were known, the presence or absence of even a rudimentary con- 
nection between the head kidney and the functional kidney was 
of considerable interest as throwing light on the probable relation 
between the two; but in view of the solution of this part of the 
problem furnished by embryology this ceases to be of any particu- 
lar significance. 
A study of sections shows that the main body of the gland is 
made up of numerous tubules which open through narrow nephros- 
tomes into the pericardial cavity, and, passing inwards, unite 
with one another, and finally with the central duct (fig. 2). New 
tubules are being formed throughout life. These branch out from 
the old tubules just back of the nephrostome, and while still very 
short acquire an opening into the pericardial cavity. The new 
tubules, along with all the rest, grow in length, and may in the 
course of time give rise by branching to still other tubules. It 
seems certain that new tubules never grow out from the central 
duct. - If all the tubules in the adult are derived by branching 
