662 JULIAN 8. HUXLEY 
encircled the zooid. The actual origin of the branch could not 
be traced in vivo. When old zooids die, stolon branches 
will frequently grow into the test previously occupied by the 
zooid. 
(g) Death-changes.—Death-changes in Perophora usually 
invelve a change of the green colour to a hard brown or black. 
(hk) Change of Position of Stolon.—When a stolon- 
zooid system is isolated, and new growth of the stolon with 
subsequent bud-formation takes place at one end, not only 
may the original zooid be completely resorbed, but the stolon 
tissue may abandon the original region and become con- 
centrated in the region of the new bud. This ‘ moving-on’ 
of the stolon is common in regeneration in Hydroids. 
(1) Segmentation of Stolon.—In not very dilute 
solutions of KCl and KCN in which the stolons were affected, 
the stolon-tissue sometimes contracted into a series of separate 
ellipsoid portions giving the appearance of a necklace without 
a string. 
7. KXPERIMENTS ON OTHER SPECIES. 
(a) On Amaroucium.—Some experiments were also 
made on a form of compound Ascidian very abundant at 
Wood’s Hole—Amaroucium pellucidum, var. con- 
stellatam. For information and advice as to this form 
[ have to thank Professor Caswell Grave. 
Twenty small pieces of Amaroucium colonies, consisting 
each of from two to twelve or fifteen individuals, were cut 
out and placed in separate dishes in a small volume of water. 
The experiment was started on July 11 and was terminated 
after twenty-nine days. Controls were kept in the circulation- 
tanks. 
Those kept in the unchanged small volumes of water showed 
alterations as follows. The larger pieces remained normal 
longer than the smaller. The larger individuals, however, 
usually showed reductional changes sooner than the smaller, 
ceteris paribus; but they did not usually remain as 
healthy as the small ones during reduction. Often they 
