214 



J. S. HUXLEY. 



mental animals were for practical purposes all healthy plutei with 

 well-developed arms. 



D. Four-day plutei transferred to 72/3,000,000 and 72/4,000,000 

 HgCl 2 . After 24 hours, all appeared normal, and about 90 per 

 cent, were still swimming. After 48 hours, all had sunk to the 

 bottom, ciliary action was somewhat reduced, there was a slight 

 general shrinkage and loss of transparency as compared with the 

 controls, and the arms had become slightly though definitely 

 shorter, but without protrusion of the skeleton. The experiment 

 was here discontinued, after another series had been started. 



E. Five-day plutei (a) to HgCl, 72/1,000,000, (&) to HgCl, 

 w/2,ooo,ooo, (c) control in same amount of outside sea-water. 



The controls remained healthy, with long arms, throughout the 

 first 4 days of the experiment. The results may be tabulated as 

 follows : 



TABLE I. 



(a) 



24 hrs. 



1,000,000 



All at bottom. Marked arm- 

 resorption ; no protrusion of 

 spicules; arms mere knobs or 

 Y^ to y 2 normal length ; aboral 

 end usually swollen. 



48 hrs. Still further arm-resorption. 



72 hrs. Arms absent or only knobs ; a 

 few with total dedifferentiation 

 of oral end ; many with aboral 

 end no longer swollen, mesen- 

 chyme clumped, gut shrunken, 

 spicules sometimes just pro- 

 truding. 



96 hrs. Spicules often protruding, 

 most showing disintegration at 

 oral end, and narrow form of 

 body. 



120 hrs. Dead. 

 144 hrs. 

 168 hrs. 



(6) 



2,000,000 



All at bottom. Moderate arm-re-' 

 sorption ; no protrusion of spicules. 



Slightly more resorption than at 

 24 hours. 



Slightly more resorption than at 48 

 hours. 



Condition as in (a) after 24 hours. 



Condition as in (a) after 48 hours. 

 Condition as in (a) after 96 hours. 

 Dead. 



(a) / 1, 000,000. Some individuals after 24 hours in the 

 medium are represented in Fig. i. 



