STUDIES IX ARTIFICIAL PARTHENOGENESIS. 173 



These facts enable us to interpret many of the results of Loeb 

 and Robertson on a truly chemical basis, and without the aid 

 of a hypothetical lysin. But there is also another factor to be 

 considered in the analysis of the action of sera, and tissue ex- 

 tracts. It is the fact that many proteins are probably able 

 to effect a swelling of the vitelline membrane. Such an action 

 is at least true for egg albumen. The eggs of 2 females were 

 washed twice and pipetted into 100 c.c. of I per cent, egg al- 

 bumen in sea-water. Before ten minutes had elapsed the mem- 

 branes on most but not all of the eggs had swollen considerably. 

 The swelling action of albumen seems to vary considerably, 

 sometimes being almost negligible. It is, I think, to be regarded 

 as a phenomenon akin to peptonization, the albumen playing 

 the part of a protective colloid. 



KCN. The action of potassium cyanide is rather difficult to 

 explain on basis of the surface-tension theory. Although KCN 

 alone, in the dilutions used, never caused elevation of the mem- 

 brane, if the solution was made hypertonic the membrane did 

 separate from the egg. Thus on July 31, 1914, membrane ele- 

 vation did not occur in 25 c.c. of sea-water plus I c.c. of 1/20 per 

 cent. KCN, but in a similar solution plus 4 c.c. 2.5 M NaCl, the 

 vitelline membrane in practically every case became lifted away 

 from the egg surface. How can this observation, which was 

 repeated several times, be interpreted on the basis of the surface- 

 tension theory? As is well known, KCN hydrolizes readily, 

 so that KOH and HCN are always present in a solution of the 

 cyanide. Probably HCN plays the most important part, for 

 it is a gas, and hence its surface tension is practically zero. 

 Thus it no doubt lowers the surface tension of the vitelline mem- 

 brane (cf. p. 166). But membrane elevation does not result, 

 because of another effect of the cyanide. In the first paper 

 of this series, it was pointed out that even if a substance lowered 

 surface tension, it would not produce membrane elevation if it 

 increased too greatly the modulus of elasticity of the vitelline 

 membrane, for in that case the toughened membrane would be 

 incapable of stretching. There is evidence that KCN actually 

 does increase the modulus of elasticity. In the next section it will 

 be shown that the presence of KCN retards membrane swelling, 

 and such anti-swelling action is a general characteristic of all 



