157] 



THE GOLDFISH AS A TEST AN IMAL— POWERS 



37 



trations (0.66 to 0.25 N. See Table XXV) increased with decrease in concen- 

 tration. The shortest survival time of any goldfish was 30 minutes. From 

 this point (0.25 N.) the toxicity of the CuCl2 decreased with decrease in con- 

 centration but the decrease was very slight as compared to the dilution until 

 the maximum survival time of the goldfish was 430 minutes. With the CdCl2 

 there was also an increase in toxicity with a decrease in concentration with the 

 highest concentrations tested (0.157 to 0.078 N. See Table XXVI). The 

 two goldfish died in 42 and 43 minutes in 0.078 N. CdCU. From this point 



TABLE XXVII 

 Ferric CHLORmE. Temperatxjke 21.5° C. 



the toxicity decreased very slowly in proportion to the dilution of the solution 

 until the maximum survival time of the goldfish was 1080 minutes inO.lSX 

 10"^ N. The toxicity of the FeCls, unlike CuCl2 and CdCl2, decreased pro- 

 gressively with the dilution of the solution from the highest concentration 

 (0.284 N. See Table XXVII) to the lowest concentration (0.166X10-3 N.) 

 tested when the survival time of the goldfish reached a maximum of 1200 

 minutes. 



The variations of the toxicities of these three salts from that of other 

 substances tested can possibly be explained by the fact that they form colloidal 



