PAR THENOGENESIS 



Among the cytolytic (and haemolytic) agents named by 

 Loeb are i}4 M NaCl and distilled water. Now I find that 

 either of these induces membrane-separation in Arhacia- 

 eggs while the eggs are in the solution.^ In a pure 2I2 M 

 NaCl solution the membranes separate with extreme rapid- 

 ity,- so that to follow the process one must use a less con- 

 centrated solution. The separation of the membrane in 

 hypertonic sea-water is due to the rapid shrinkage of the 

 egg-plasma. In distilled water, on the other hand, the 

 eggs distend as water enters but the elastic vitelline mem- 

 branes distend more rapidly than the plasma so that in five 

 seconds the membranes are off the eggs, at which time the 

 plasma shows no sign of disruption. With prolonged expos- 

 ure the egg-plasma swells and reaches the membrane; 

 cytolysis follows. The action of butyric acid in causing 

 membrane-separation resembles neither that of hypertonic 

 nor that of hypotonic sea-water. In my experience all of 

 the cytolytic agents named by Loeb fall into two classes: 

 those that do not call forth membrane-separation directly 

 but only after they are washed away by transferring the 

 eggs to normal sea-water; and those that do act directly, 

 by producing either shrinkage of the egg-plasma or exten- 

 sion of the elastic membrane. If the spermatozoon's first 

 duty to the egg be to inject a lysin, which of the three 

 kinds of cytolysis — that of butyric acid, of hypertonic sea- 

 water or of hypotonic sea-water — does this behavior of the 

 spermatozoon resemble t 



An agent which induces membrane-separation in the sea- 

 urchin's egg can not act as a fatty acid, a concentrated neu- 

 tral salt solution and distilled water at one and the same 

 time. If we consider all the cytolytic agents which have 

 been employed, we fail to discover in their mode of action 



^ Just, ig22a, ig2Sc. 



- Just, unpublished observations. 



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