DZ SELIG HECHT 
The difference in the elastic response of the test to strains of 
short and long duration may be the explanation of the distorted 
appearance of many laboratory and museum specimens. The 
collection and transportation of living animals involve a continued 
stimuiation. This results in the maintenance of the curved 
condition for a long time, until finally the elastic limit is passed, 
and the animal remains permanently abnormal in appearance. 
The elasticity of the test is further made use of in the third 
type of movement of which Ascidia is capable. This is a con- 
traction of the body along its dorso-ventral axis, in such a way 
that the right side forms the concavity. The muscles which 
are concerned are the transverse fibers on the right side (fig. 9). 
In order that they may exert their influence, the test is thinned 
& 
a b Cc 
Fig. 12 Transverse sections of test. a, near tip of oral siphon; b, near base 
of oral siphon; c, through middle of body. 
out along a narrow line, in the middle of the right side, running 
parallel to the long axis. The contraction of the transverse 
muscles bends the test along this line, with the consequent forma- 
tion of two prominent cheeks (figs. 5 and 12c). 
The contraction of the body on its dorso-ventral axis extends 
in some cases well into the oral siphon. There are circular mus- 
cles present in the siphon, which by their contraction can de- 
crease its diameter. Here also the test shows.an arrangement 
of thick and thin portions on the right side, whereas the left 
side still maintains its uniform thickness in order to aid in the 
recovery (fig. 12b). 
It is consequently obvious that the test is intimately concerned 
in the contraction of the body on its short axis. The same is 
true for the siphon rim movements and especially for the bending 
of the body on its long axis. Definite structures in the test go 
