692 JULIAN 8. HUXLEY 
7. Testis. A=germ-cells, B=interstitial tissue, C—=Connective 
tissue. 
(a) Normal, (b) Transplanted, after (c) Ditto, after longer 
short period, period, 
A w AY 
Y) B+ a= < 
(B) V C++ 
v (C+) 
(C) 
8. Amblystoma limb-buds. A,=transplanted limb-bud, A, = 
regenerated remains of limb-bud in original position. 
(a) After trans- (b) End-result (ec) After trans- (d) End-result 
plantation to a from (a), plantation to a from (c). 
distance of more distance of less 
than four seg- than four seg- 
ments, ments, 
Ay A’, A; A’, 
Ay AY (A,) AR 
9. Metamorphosis of Echinoids. A=larval tissues, B=adult 
tissues. 
(a) At the time when (b) Shortly after. (c) End-result. 
larva sinks to bottom, 
A (A’) AA 
Ny i 
B B B 
9. SUMMARY. 
1. The social Ascidian Perophora viridis may dedif- 
ferentiate in either of two distinct ways, or by a mixed method : 
(a) by reduction to a spheroidal mass, as in Clavellina ; (b) by 
incipient reduction as in (a), but followed by total resorption 
into the stolon, which may grow during the process. 
2. Resorption is due to the migration of the individual cells 
out of the tissues into the haemocoel. 
3. In certain conditions the zooid maintains itself, in spite 
of food not being provided, at its original size and in perfect 
health. This it does by resorbing the stolon. 
4. Experiments with dilute solutions of KCN show that 
resorption of the zooid occurs in slightly unfavourable condi- 
tions, which affect the sensitive zooid more than the less 
highly-organized stolon. 
