9 6 



HIKOKURO HOXDA. 



TABLE I. 



AVERAGE TIME IN MINUTES REQUIRED TO CAUSE CESSATION OF ALL MOVEMENTS. 



Is this resistance of Rhabditis due to a mechanical reason or to 

 the ability of the animal to neutralize acids? The results of the 

 experiments with toxic substances (Table II.) seem to show that 

 the first is the case, since Rhabditis is the most resistant of the 

 five forms studied not only to acids, but to the other toxic sub- 

 stances as well. If this presumption is correct, the cuticle with 

 which Rhabditis is covered may be supposed to prevent the pene- 

 tration of the toxic substances. 



TABLE II. 

 AVERAGE TIME IN MINUTES REQUIRED TO CAUSE CESSATION OF ALL MOVEMENTS. 



We notice in these tables that Rhabditis is about 2.5 times as 

 resistant to N/4O NaOH, 0.05 per cent, mercuric chloride and 

 N/ioo HO than is Daphnia, the next most resistant form. Tad- 

 poles died more quickly in N/2O NaOH than in N/2O HC1. As 

 shown in Table II., tadpoles died in 2 minutes in X 40 NaOH, 

 while they died in about 4 minutes in \ 3oHCl. This is probably 

 due to the fact that the acid coagulates the body proteins as it 

 penetrates, \vhile the NaOH dissolves them. Tadpoles, which 

 were placed in the 5 per cent, solution of ether for 5 minutes, 

 revived though they were in a very bad condition. None of the 

 Rhabdites revived after placing them 30 minutes in the solution 

 of ether. 



In order to study the penetration of an intra-vitam stain, some 



