DEDIFFERENTIATION IN PEROPHORA 659 
of the network of small blood-vessels close to the surface 
with the green blood-corpuscles. This gives. a premature 
green opacity to zooids dedifferentiating in KCl. This animal 
was dead on the succeeding day. 
In the solution with 4 ¢.c. one died, after only slight reduction, 
after three days. The other exhibited dedifferentiation of a type 
very similar to that just considered, but this time accompanied 
by a little growth in the stolon, which remained healthy and 
tonic. Although reduction had started, resorption never 
ensued, and after five days the zooid had died and was repre- 
sented by a blackish spheroidal mass about half its original 
diameter, while the stolon was still healthy. (Fig. 19.) 
In the solution with 2 ¢.c. matters were very similar. The 
stolons remained healthy, though distended with blood-cells 
(and possibly others) from the zooids, for over five days. The 
zooids withdrew their siphons from the test, shrank, and 
became opaque (i.e. started to dedifferentiate), but died with 
change of colour to brown or blackish before any marked 
resorption had occurred. 
It will thus be evident that there are at least two factors 
concerned in resorption in Perophora. The first is the shrinkage 
of the whole organism and reversion of its cells to a cuboidal 
type which we may call simple dedifferentiation, the second 
is the migration of cells out of the tissues, which does not take 
place, or takes place only to a negligible degree, in the absence 
of the circulation. 
Thus in the presence of KCl, with consequent cessation of 
heart-beat, the aspect of the process is altered in many parti- 
culars. High concentrations of KCl damage both zooids and 
stolon, and both contract. The cessation of the circulation in 
lower concentrations leads to a very speedy dedifferentiation of 
the zooid ; but this never goes very far before death supervenes, 
and is unaccompanied by resorption. 
The experiments were repeated, with variations, with 
forty-five more specimens; essentially similar results were 
obtained. Twenty of these showed dedifferentiation without 
resorption. In addition one showed a slight, one a moderate, 
