CHAIN OF CYCLOSALPA AFFINIS 417 
b. The peduncles and foot-preces. These structures play so 
important a réle in the production of the wheels that they must 
be described in some detail. Almost all the figures show the pe- 
duncle in one stage or another. Fig. 12, best gives its relation to 
the full grown zooid, showing that it is a thin flap or sheet extend- 
ing out from the ventral median line. The diagram (fig. 17) 
shows that the peduncles of the series are parallel throughout the 
first part of the chain, and that each by means of its ‘foot-piece’ 
(fp.) is in contact with four others, its two neighbors in each row. 
These foot-pieces are also well shown in the right-hand portion of 
figs. 19 and 22. As the zooids grow and extend out farther from 
the blood vessel, the peduncles lengthen, and the foot-pieces 
grow longer as the zooids grow wider, at least until the region of 
the twist is reached. 
Along with the great increase in the size of the zooids and the 
development of the peduncles comes a change in the circulatory 
system. The two individual blood vessels coalesce to form one 
vessel with two channels (fig. 24, zbv.). The blood current has the 
same course as before except that the incoming and outgoing 
currents of each zodid pass through one vessel. Observation of 
the blood currents in the living animals made the task of working 
out the circulation much easier and more certain than it would 
have been if confined to preserved specimens. The cross section 
(fig. 25) shows well the relation of the zooids to the blood vessel, 
the foot-pieces joining the zooids above the vessel, (fp.) and the 
individual vessels leading from the zooids to the two parts of the 
large vessel (zbv.) 
c. The emergence of the chain to the outside world. Through the 
first part of its course, the chain is enclosed within a definite 
tube in the test just below the endostyle, this tube ending at a 
point just posterior to the placental vessel and anterior to the first 
body muscle band. This first muscle bends posteriorly here so 
that its insertion is along the lower part of the tube opening. 
The placenta usually disappears before the chain reaches this point. 
There seems to be more or less of a cavity left in the test where 
the placenta was, and the chain, as it reaches this point, no longer 
being held in its horizontal position by the tube, following the 
