236 SELIG HECHT 
The edges of the old test gape at the injured region, and the new 
test which is formed underneath them is continuous with the 
old test where the two meet close to the mantle tissue of the 
animal. } 
It was impossible to secure complete regeneration in an animal 
whose entire test had been removed. This was due solely to a 
deficiency in technic, and not to an incapacity on the part of the 
animal. The seawater supplied to the laboratory. contains 
almost no plankton organisms, and since these furnish the food 
supply of Ascidia, even perfectly normal animals died after a 
week or more of laboratory confinement. I was unable to devise 
a method of keeping animals without a test out in the open water, 
because they could not be attached to anything. Consequently 
it was possible to observe them only for a few days in the labora- 
tory. Here they showed the usual beginnings of regeneration. 
After a day, a thin layer of test material was formed on the right 
side of the body and on the entire surface of the siphons, but 
not on the surface of the renal body. Soon the cellulose began 
to extend over to the left side, making the bare region smaller 
and smaller. Undoubtedly, under better conditions, a complete 
test would have been regenerated. 
The newly formed test material is pigmented in the usual way. 
The pigmentation is not dependent on the presence of light. 
Animals whose tests had been removed at night, were kept in 
complete darkness for several days. They regenerated as usual, 
and the fresh test contained the blue pigment. Moreover, a 
new, pigmented test will form on the right face of the animal 
under the intact, opaque, old one, when the latter has been 
accidentally separated from the eetodermal surface which secretes 
it. Therefore the formation of a pigmented test is not the result 
of a photic stimulus only. 
These regeneration experiments, as well as the phenomenon 
of sloughing, indicate that normally there is a continuous addi- 
tion to the thickness of the test, in order to compensate for the 
disintegration of the exterior, and for the changing size of the 
animal. ’ 
