208 



ANIMAL AGGREGATIONS 



freshly prepared suspensions of 2 drops of colloidal silver in 50 cc. 

 of sea-water. All conditions were similar. The temperature was 

 18.5° C. The results are summarized in Table XX. 



If Drzewina and Bohn were correct in thinking that the colloidal 

 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 the used sub- 

 stance, it was necessary to add the same amount, i drop of colloidal 



TABLE XX 



Showing Righting Time of Ophioderma after an Exposure of 17 Hours in 



Reconditioned and Fresh Suspensions of Colloidal Silver 

 All gave the righting reaction. 



silver per 25 cc. to this suspension, in order that it might be as 

 deeply colored as was a fresh suspension made up with that amount 

 of the colloidal silver. There was only sufficient colloidal silver left 

 in this twice-used suspension to discolor the liquid. Either the 

 animals or the aeration, or both, had removed the greater part of 

 the silver; and it can be readily demonstrated that the effect was 

 not wholly due to aeration. The water thus treated was distinctly 

 sirupy, and evidently held organic matter, received from the two 

 lots of Ophioderma which it had contained. 



The effect of this twice-reconditioned suspension was tested as 

 before. Comparison tests were run with newly prepared suspen- 

 sions, and the results are summarized in Table XXI. 



There is no evidence here of the presence of an autoprotective 



