PHYSIOLOGY OF ASCIDIA ATRA LESUEUR 235 
The test shows a ragged surface undoubtedly representing the 
places where it had been torn. Such a test is highly instructive. 
In cross section (fig. 2).1t can be seen that regeneration had not 
taken place by the mending of the injured edges, but by the 
growth of the new test around the body tissue. It does not 
seem as if the injured portion had been specially reconstructed; 
but rather as if the test material had been secreted by the sur- 
face generally, and only incidentally covered the injured part. 
These appearances may be duplicated experimentally. Asci- 
dians present varying degrees of ability to regenerate the test. 
Some, like Cynthia and Phallusia, seem incapable of surviving 
Fig. 2 Sketch of regenerated animal. The transverse section of the test 
shows the mode of regeneration. 
even partial removal of it (Fol, ’08).  Ascidia atra, however, 
not only recovers rapidly after portions of the test have been 
removed, but it makes good such deficiences in a short time. 
It has been described how, within a day after the removal 
of a section of the test, there has already been secreted a thin 
layer of cellulose. This film is continuous with the innermost 
surface of the uninjured test, and adheres closely to the soft 
tissue which has formed it. Animals in this condition, when 
placed in a sheltered position in the natural environment of the 
species, continue to thicken the film until it assumes the ordinary 
dimension of the test. In one animal, for example, a hole several 
centimeters square was mended in two weeks. Sections of such 
tests are identical with those of animals like the one in figure 2. 
