234 SELIG HECHT 
captivity was the result of the change of these granules to a 
deep blue. The figures which he gives (Caullery, °95, fig. 52 
for these cells resemble the blood cells of Ascidia and of ascidians 
in general (Cuénot, 791). The color change in Botrylloides is 
artificial; in Ascidia atra it is in the regular course of events. 
3. Formation of the test 
Freshly collected specimens of A. atra, as well as animals in 
their natural surroundings, possessed a bright and clean appear- 
ance, which was often lost in the laboratory in a short time. In 
confinement, the outer surface of the test soon changed to a dull 
gray. The gray material was gradually sloughed, coming off 
in shreds, and resembling a human skin peeling after a sunburn. 
Although the layers were removed by the movement of the water, 
more appeared in a short time, and the animals continued to 
shed the outer portion of the test as long as they remained in the 
laboratory. 
The animals were kept in battery jars of about ten liters 
capacity, into which the seawater flowed in a gentle stream. 
Under such circumstances, the water surrounding the animals 
had but little motion. This is quite in contrast to the compara- 
tively turbulent conditions to which the species is normally 
subjected. Consequently, it seemed probable that the ap- 
pearance of the test was merely a superficial laboratory product, 
and not due to any real effect on the animal. Indeed, individuals 
kept in smaller jars, in which a more vigorous current was 
present, showed little sign of this surface change. The sloughing, 
therefore, merely indicates that Ascidia renews its test continu- 
ally by secreting fresh test material on the inside, and allowing 
the outside surface to disintegrate and to be removed by the 
action of the waves. 
This conclusion is strengthened by the phenomena which 
attend the regeneration of the test. Occasionally animals were 
collected which showed an appearance that can be interpreted 
only as a regeneration of the test and perhaps of other structures 
(Hirschler ’14). Figure 2 is a sketch of such an individual. 
