480 



J. S. HUXLEY AND G. R. DE BEER 



In order to see whether any of the results obtained were due to 

 the specific effects of KCN, experiments were also made w^ith 

 HgClg. When solutions of N/1,000,000 and N/2,000,000 were 

 used, the resorption effects were identical with those in KCN. 



After varying periods in solutions of all the strengths, some 

 preparations were removed and placed in clean fresh sea-water 

 with a view to inducing them to cease resorption and reform 

 zooids. In no case was this successful. The preparations ceased 

 resorption for a short time, but then continued. This was to 

 be expected from the behaviour of zooids in normal sea-w^ater. 



When the zooid is severed from the stem at the base of the 

 hydrotheca, the preliminary dedifferentiation occurs as u§ual ; 

 but after a certain number of cells have migrated into the 

 interior there is no room for more. The result is an ovoid 

 dedifferentiated mass, tightly packed with cells (Text-fig. 6). 

 Similar phenomena were seen in Perophora. Thus the degree 

 of resorption depends on the amount of space available. Resorp- 

 tion will only proceed to a limit when the migrating cells are 

 removed. A parallel is here provided with those chemical 

 reactions which will only proceed to a limit if the products of 

 the reaction are removed. 



Histology. 



In the previous section the various stages of resorption were 

 briefly described. The actual route of migration of the cells 

 is, of course, through the gastro-vascular cavity (PI. 26, figs. 2, 



