586 JACQUES LOEB 



24 minutes : Many eggs develop into larvae which rise to the surface 

 32 minutes: Few eggs develop into larvae. The majority disintegrate 

 45 minutes: All form membranes and begin to develop, but disintegrate 

 60 minutes: Like the preceding lot 

 (b) Eggs in 0.3 cc. to" NHaOH for thirty minutes and subsequently in the neu- 

 tral hypertonic solution for 



10 minutes : About 10 per cent of the eggs form membranes and develop 



into perfect larvae 

 15 minutes: Practically all the eggs develop into swimming larvae, many 



of which are perfect. Numerous larvae rise to the surface 

 23 minutes: Very few eggs develop into larvae; the majority of the eggs 



undergo cytolysis 

 45 minutes: All the eggs undergo cytolysis 



It is, therefore, obvious that the eggs that had been in 50 cc. 

 m/2 (NaCr + KCl + CaClo) + 0.3 cc. ^ NH4OH for ten min- 

 utes developed best when exposed to the hypertonic solution 

 for twenty-four minutes, while an exposure of sixteen minutes 

 was too short and one of thirty-two minutes too long. The 

 eggs that had been in the same alkaline solution three times 

 as long (thirty minutes), developed best when put for fifteen 

 minutes into the neutral hypertonic solution, while ten min- 

 utes were not quite sufficient and tw^enty-three minutes too 

 long. 



These observations throw' a light on the experiment men- 

 tioned in the previous paragraph. In this experiment the 

 eggs were put into an NH4OH solution containing KCN for 

 forty-five minutes. The latter retarded the oxidizing effect 

 of the NH4OII amd therefore had the same effect as if the eggs 

 had been put for a shorter period into an NH4OH solution free 

 from KCN. We have seen, however, that a shorter exposure 

 of the eggs to a solution of NH4OII requires a longer exposure 

 than fifteen minutes to the hypertonic solution if we wish to 

 cause the development of the eggs into larvae. The eggs did 

 not develop in this experiment because the exposure of fifteen 

 minutes to the hypertonic solution was in this case too short. 



This idea was put to a test. The unfertilized eggs of Arbacia 

 were put for forty- two minutes into a solution of 50 cc. m/2 

 (NaCl + KCl + CaClo) + 0.3 cc. ^ NH4OH + 5 drops 0.1 

 per cent KCN. They were then transferred directly into the 



