86 C. M. CHILD. 



perisarc; in the thin perisarc of the more apical regions the 

 resulting color is scarcely appreciable, but the thicker perisarc 

 of the more basal regions, which is normally yellowish or brownish 

 in most forms, appears more deeply colored in the permanganate, 

 probably because of its greater thickness. In no case observed, 

 however, is reduction in the perisarc sufficient to obscure the 

 progress of coloration in the ccenosarc. 



The permanganate penetrates the perisarc rather rapidly. 

 The apical regions enclosed in very thin perisarc begin to stain 

 almost as soon as the naked parts. Penetration of the thicker 

 perisarc of the more basal regions occurs somewhat more slowly, 

 though even in these regions the perisarc is far from being im- 

 permeable. Because of the presence of the perisarc and its 

 different thickness at different levels, difference in rate of reduc- 

 tion and staining of intact stems cannot be regarded as a safe 

 criterion of the differences in physiological condition. This 

 difficulty, however, is easily avoided by using pieces of stems from 

 different levels with fresh transverse cut surfaces. Pieces from 

 different levels may be placed side by side in permanganate and 

 the rate of coloration of the exposed distal or proximal ends 

 directly compared. In this way it is readily determined that a 

 gradient in rate of reaction is present in the stems. This gradient 

 is much less steep than that of hydranths and growing tips, for 

 reduction occurs relatively slowly in all stem regions, but with 

 differences in level of 10-15 mm. or more it is appreciable, and 

 between stem levels near the apical and those near the basal end 

 of colonies several centimeters in length the difference is marked. 

 In such cases the more apical level usually becomes distinctly 

 yellow or even brownish before the more basal level is appreciably 

 colored. 



In preparations of whole colonies or of the longer branches, 

 cleared after completion of reduction, the stems may remain 

 opaque throughout if the colony is well fed and the ccenosarc 

 thick, but in most cases a distinct basipetal decrease in opacity 

 appears. In order to make certain that such differences are not 

 merely apparent and due to differences in transverse diameter 

 of the perisarc, it is desirable to compare regions from the 



