ACTIVATION OF STARFISH EGGS BY BUTYRIC ACID. 147 



temperatures upon tropical marine animals 1 or warm-blooded 

 vertebrates. Greeley describes protoplasmic condensation and 

 loss of water in Stentor and other organisms as a result of pro- 

 longed exposure to low temperatures (6 and lower in most of 

 his experiments), and he calls attention to various resemblances 

 between the effects produced by cold and by hypertonic solu- 

 tions. 2 It does not seem probable, in the light of more recent 

 knowledge, that the activation following the exposure of star- 

 fish eggs to cold and to hypertonic sea-water respectively can 

 be referred directly to the same cause, namely, loss of water, as 

 Greeley supposed ; but the evidence that a lowering of temperature 

 below a certain critical point produces definite structural alter- 

 ations has an obvious bearing on the present problem. In the 

 case of high temperatures (above 30) the activating influence is 

 probably to be referred to structural changes in the protoplasmic 

 system, as the temperature-coefficients indicate; and the same 

 appears to be true for cold. Changes in the physical condition 

 of the structural colloids e. g., gelation, dehydration, altered 

 aggregation-state may alter locally the permeability or other 

 properties of the protoplasmic system (e. g., of membranes or 

 other barriers to diffusion), and thus render possible interactions 

 which are not possible at ordinary temperatures. This seems 

 to be the most consistent general explanation for the fact that in 

 the starfish egg temperatures both above and below a certain 

 range, 8 to 28, may induce activation. This range may be 

 regarded as corresponding to the range of stability of the struc- 

 tures concerned. 



GENERAL DISCUSSION. 



The phenomena under consideration in the present paper 

 exhibit many features in common with those accompanying or 

 conditioning cytolysis in other cells. Cytolysis in weak solutions 



1 The tropical medusa Cassiopea shows an interesting parallel to the conditions 

 in starfish eggs. The animals may be cooled to 9.5 and recover, if immediately 

 returned to sea-water at the normal temperature of 29; but if cooled to 7 or 8 

 there is no recovery; some irreversible change is produced and the tissues disinte- 

 grate on return to warm water (E. N. Harvey, "Effect of Different Temperatures 

 on Cassiopea," Carnegie Institution Publications, 1910, No. 132, p. 32). 



2 Greeley, Amer. Journ. Physiol., 1902, Vol. 6, p. 122; BIOLOGICAL BULLETIN, 

 1903, Vol. 5, p. 42. 



