GLOCHIDIA — FACTORS UNDERLYING ENCYSTMENT 481 



Essential oils 



Oil of cloves and wintergreen, in saturated aqueous solution, cause 

 glochidia to close with great promptness and vigor. These are odorous 

 substances which possibly are effective as irritants. 



Salts 



A comparative test was made with the neutral halogen salts of potas- 

 sium, to discover among other points the relative stimulative efficiency 

 of the anions. 

 KCl: 



N/100. All respond immediately. 



N/250. Closure progressive during five to ten minutes. 



N/400. Most close within ten minutes but some do so slowly and 

 deliberately. 



N/600. Some are closed at the end of ten minutes; most remain 

 open. 

 KBr: 



N/4. Effective at once. 



N/50. All close, some a little tardily. 



N/100. Affects samples from two mussels rather strongly; in another 

 sample the response is weak, but quite general in five minutes. 



N/250. Little or no effect. 

 KI: 



N/25. All close. 



N/100. Affects relatively few. 



N/300. A very few close. 



N/500. Practically no response; after an interval a few shut. 



A comparison was also made of the stimulative efficiency of the ka- 

 tions of the alkali metals and also of the divalent kations, Mg and Ca. 

 KCl: (Vide supra.) 

 NaCl: 



N/4. Effective. 



N/10. All close, but rather slowly. 



N/25. Closes half of one lot and all of another in ten minutes. 



N/50. No response in ten minutes. 

 LiCl: 



N/4. All closed, but after a distinct latent period of five to ten sec- 

 onds or more. 



N/10. One lot responded fairly promptly; another slowly, after 

 several minutes. 



N/25. After five minutes a few begin to contract, but the response 

 is not general. 

 MgCh: 



5N. All close at once. 



IN. Some shut immediately, the remainder gradually. 



N/4, Same as IN; action not rapid. 



N/10. A few respond in one lot; practically none in another. 



