PHYSIOLOGY OF ASCIDIA ATRA LESUEUR 249 
(fig. 9). In the living animal this side of the body adheres firmly 
to the test. The left side, however, which includes the renal 
organ, parts of the intestine, etc., is free from the test, the two 
being connected only by a single blood vessel. Consequently 
any contraction of the long muscle strands on the right side will 
result in a bending of the body and test in that direction. This 
is facilitated by the fact that the right side of the test is much 
thinner than the left (fig. 10). 
The bending of the body on its long axis is always associated 
with a movement of the siphon rims. This becomes clear when 
3 
Fig. 10 Longitudinal section of test, passing through oral siphon. 
its kymographic record is examined (fig. 8). The kink in the 
very first part of the curve denotes a siphon rim closure. It will 
be seen that the movement of the siphon precedes the vigorous 
activity of the body as a whole. 
The curve made by the bending of the body (fig. 11, curve 6) 
resembles in all essential features the one made by the siphon 
rim contraction (curve 7). It may be divided into four phases, 
the durations of which are relatively the same as in the activity 
of the siphon. The first phase is short, and accomplishes the 
main extent of the contraction. During the longer, second, phase 
a slower activity brings about the maximum point in the curve. 
The resumption of nearly the normal position of the body is 
accomplished in the third phase, whereas the complete relaxation 
