LARVAE OF ARBACIA PUNCTULATA 



429 



be maintained. The following percentages represent the maxi- 

 mum inhibition in each experiment when the control has reached 

 its greatest size. 



EXPERI- 

 MENT 



4 



5 

 8 

 9 

 11 

 16 

 17 

 18 

 19 

 20 

 21 



COMPOSITION 



Concentration and dilution 



Gradual concentration < 



CH3COOH 



CH3COOH 



NaHCOs 



NaHCOs 



NaaCO:, 



NaCl 0.60M 



NaClO.eOM - 



NaCl (hypertonic) 



NaCI (hypertonic) 



CO2 



Eggs X Sperm of different parentage 



PER 

 CENT 



44.1 

 34.2 



1.8 

 63.3 

 21.0 

 25.8 

 11.7 

 38.8 

 41.7 

 74.7 

 19.2 

 64.3 

 53.4 

 29.6 



3.9 



These tables show the greater plasticity of Arbacia larvae in 

 respect to decrease in size than in respect to increase. In 

 practically all of these solutions, while the larvae had departed 

 widely from the normal in the characters distinctive for the 

 various substances employed, they seemed vigorous and cap- 

 able of continued development. To what extent they could 

 resist new adverse conditions that might be superimposed, or 

 to what extent they could survive these same conditions at a 

 later period has not been determined in these experiments; but 

 these figures indicate to some extent the range of variation 

 which may possibly occur in Arbacia larvae during early stages 

 in their natural environment. 



