3 o8 



\V. C. ALLEE AND J. F. SCHUETT. 



rapid cine lit, une substance (ou des substances) qui a pour effet 

 de les proteger." 



Wholly similar experiments were run with the brittle starfish, 

 Ophiodcnna, to test for the presence of the postulated auto-pro- 

 tective secretion. Colloidal suspensions in which Ophiodcnna had 

 been exposed were reconditioned by three hours aeration with room 

 air in order that the new lot might not suffer from low oxygen 

 tension, and were filled to the original volume with distilled water. 

 The original suspension had been made with one drop of colloidal 

 silver for each 25 cc., and the same amount was added to this 

 reconditioned water. Tests showed that the aeration of freshly 

 prepared suspensions for this length of time caused a color change 

 but did not markedly affect the toxicity. 



Three lots, each consisting of one group of five bunched animals 

 and four isolated individuals, were placed severally in 50 cc. of 

 such a reconditioned suspension, nine hours after the previous ex- 

 periment had closed. These were run simultaneously with three 

 similar lots in freshly prepared suspensions of two drops of col- 

 loidal silver in 50 cc. of sea water. All conditions were similar. 

 The temperature was 18.5. The results are summarized in Table 

 II. 



TABLE II. 



SHOWING RIGHTING TIME OF Ophioderma AFTER AN EXPOSURE OF 17 HOURS IN 



RECONDITIONED AND FRESH SUSPENSIONS OF COLLOIDAL SILVER. 

 All gave the righting reaction. 



Reconditioned Suspension. 



New Suspension. 



If Drzewina and Bohn were correct in thinking that the col- 

 loidal silver is not removed from solution on exposure to the 

 animals, there should have been an excess accumulation of this 

 substance in the twice used water; but after again conditioning 



