c^6 H . H. Newmatt 



After 55 minutes, 8 H hybrids dead, 2 still vigorous, i H 



pure still feebly living. 

 After 65 minutes all dead. 



This experiment shows an interesting fact that there is a well 

 marked individuality among these embryos. One of the H 

 hybrids (the more resistant strain) succumbed before any of the 

 H pure (the less resistant strain) ; while one of the H pures (the 

 less resistant strain) resisted feebly as long as any of the H hybrids. 

 On the whole, however, the H hybrids showed themselves to be 

 the more resistant of the two heteroclitus strains. 



2 Experiments with KCN 



Believing that KCN acts as a reducing agent upon animal 

 tissues and produces the same effects as those produced by lack 

 of oxygen, rather strong solutions of KCN in sea-water were used 

 upon embryos and adults. 



Experi?nent i. Placed three adult males of each species in 

 a covered vessel filled with one liter of one-tenth molecular KCN 

 solution in sea-water. Results: The three F. majalis males died 

 in an average of 16 minutes; the three F. heteroclitus males died 

 in an average of 31 minutes. The same experiment was repeated 

 with three females of the two species. Results: F. majalis females 

 died in an average of 18 minutes, while the F. heteroclitus females 

 died in an average of 30 minutes. 



Evidently F. heteroclitus is much more resistant to KCN poison- 

 ing than F majalis. 



Experiment 2. Three six day embryos of each of the four 

 strains put into fir KCN solution in sea-water: 



The H pures lived for an average of 93.5 minutes. 

 The H hybrids lived for an average of 82.5 minutes. 

 The M hybrids lived for an average of 70 minutes. 

 The M pures lived for an average of 20 minutes. 



Experiment J. Same conditions as last experiment except that 

 ten embryos of each of the four strains were used. After 2 hours 



