pressure relations was not determined experimentally; the 

 minuteness of the spores must render experiments involving 

 plasmolysis exceedingly difficult with such organisms as 

 those here employed. It is pbvious, however, that the high 

 concentrations of the calcivim, magnesium and potassium 

 salts must be capable of exerting an extremely high osmotic 

 pressure if the ectoplasm of the spore is not readily per- 

 meable to them. 



From- the table of relative toxicities it may be seen 

 that the different compounds arrange themselves in the same 

 order, with the exception of HNCg, if other types of react- 

 ion to the chemLcal stimuli are taken as criteria. This 

 suggests that the physiological response of death, on the 

 one hand, and the various morphogenic responses considered 

 in this paper, on the other, are ultimately related to the 

 same properties or characteristics of the various stimul- 

 ating substances which bring them about. Copper is the most 

 toxic metal here dealt with, whether we consider its toxic- 

 ity as bringing about changes that result in death or as 

 bringing about the less final changes that lead to abnormal 

 growth. In the same way, magnesium, calcium and potassium 

 are the least toxic metals of the list, on whatever physiol- 

 ogical criterion we may base our judgement. 



