G. REVERBERI 329 



Oped, without any movement or contraction. The larvae seem to 

 be dead. That they are Uving is however shown by the fact that 

 they enter metamorphosis. The immobihty of the larvae is not 

 due to paralysis, because they do not reacquire motility if they 

 are immersed in normal sea water and are allowed to remain in 

 it for a length of time. Normal larvae, if placed in 1 X 10~^ M 

 selenite solution, do not lose their active movement even after a 

 long period. 



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Fig. 6. Phalhisia tadpoles, a, controls; b, development in 1 X 10~^ M 

 sodium azide. c, development in 5 X 10~- M sodium malonate; d, develop- 

 ment in 1 X 10~2 M azide plus 5 X 10^- M malonate. 



Eggs in weaker solutions (6X10~'*M) develop into mem- 

 brane-free larvae, which, however, have distorted tails and are 

 incapable of any movement. Their "heads" are normal. Their con- 

 dition does not improve in normal sea water. 



If the treatment is interrupted at the neurula stage (solutions 

 6 X 10~^ or 4 X 10~^ M) before any muscular differentiation be- 

 gins, larvae arise which also have abnormal tails and are deprived 

 of movement ( Fig. 5b ) . They do not recover if immersed in nor- 

 mal sea water. 



