CHAIN OF CYCLOSALPA AFFINIS 399 
The stolon originates just above the heart and extends straight 
forward along the median line. The zooids, as in other salpa 
chains, are first in single file, but at a certain point, the deploying 
point, shift to double file. The deploying point in this species 
occurs close to the anterior end of the heart, 3 or 4 mm. from the 
root of the stolon. At a point about two-thirds of the way be- 
tween the heart and the branchial orifice, the chain bends down- 
ward and passes to the outside world through an opening in the 
test. Immediately outside the opening, the chain doubles back 
under the parent and turns over so that it appears to be greatly 
twisted at this point. Before the twist, the zooids are arranged in 
two nearly parallel rows along the common stolonic blood vessel. 
After the twist, they are arranged in wheels which are connected 
tangentially and contain six to sixteen zooids each. These wheels 
show a gradual increase in size toward the distal end (fig. 11). 
MEASUREMENTS OF THE ZOOIDS, OF THE WHEELS AND OF A 
PORTION OF THE CHAIN NOT YET TRANSFORMED INTO 
WHEELS 
Serial measurements were made of the zooids of a number of 
chains with and without wheels as well as of the zooids of separate 
wheels. Lengths only were taken. 
The measurements of the wheels were made with dividers 
and the results are given in millimeters. Those of the unbroken 
chains were made with the micrometer eyepiece used in the Zeiss 
binocular microscope. A unit in the tables represents 0.1 mm. of 
actual length. 
The zooids of Chain I were separated from the chain for measure- 
ment, but the others were measured while still on the chain. It 
appeared that the latter is the more accurate method, since separa- 
ting the zooids, besides being a tedious process, is apt to distort and 
mutilate them. In these measurements, the posterior extremity 
was taken at the atrial orifice. The intestine was not included, 
as a slight difference in its inclination would make a difference in 
the apparent length. 
In table 1 are given the lengths of the zooids of the unbroken 
portion of Chains I-VII. Table 2 gives the same data for the 
