660 JULIAN 8. HUXLEY 
degree of resorption. Twelve formed new stolon outgrowths of 
fair length. The solutions used were 2 ¢.c. and 4 ¢.c. n/2 KCl 
in 50 ¢.¢. sea-water. 
5. ExperIMENtTS witH Low ‘l'EMPERATURE. 
Hight vessels, each contaiming several individuals, were put 
in an ice-chest, with a temperature of 3° to 8° C. 
Several points were noted when these were examined eight 
days later. Over half had turned brown or blackish, and were 
dead or dying. No cases of extreme or even considerable 
resorption were found. Most healthy-looking individuals had 
shrunk and become opaque, i.e. had dedifferentiated. The 
opacity was more marked than usual. Usually, however, the 
siphons were left open and attached to the test at a stage when 
at room-temperature they would have been closed and with- 
drawn. The heart-beat was very slow or absent, though the 
heart was usually visible. Sometimes the heart-beat began 
again soon after transference to room-temperature for examina- 
tion. Very young individuals were less dedifferentiated than 
older ones. | 
The stolon seemed to be unaffected, and often remained 
of normal appearance even when the zooid was dead or dying ; 
no new growth, however, was ever seen. Recovery did not 
occur at room-temperature. 
Here again it is clear that the zooid has been much more 
affected than the stolon, and that the slowing or cessation of 
circulation has, as in KCl, prevented resorption. 
In one system a new bud was produced on return to room- 
temperature, and grew to a normal zooid after six days. 
6. MiscELtuANEous NovTEs. 
(a2) Tone of Stolon.—The turgescence of the stolon 
appears to depend on two quite different causes—first the 
physiological condition of the ectoderm cells, and secondly 
the pressure of the blood. Observation on a stolon which was 
undergoing retraction showed that the ectoderm cells were 
capable of great passive extension. At intervals the tip of 
