35^ E. ISlewton Harvey 



3 The chemical nature of the membrane. 



4 The migration of the pigment granules of Arbacia eggs. 



5 Loss of pigment in Arbacia eggs. 



6 Surface tension changes in fertilized and unfertilized eggs. 



7 The action of development-starting substances in general. 



I. THE EFFICIENCY OF ACETIC ACID IN FORMING MEMBRANES 

 AT DIFFERENT TEMPERATURES 



A well known method of determinmg whether a given process 

 occurring in organisms is chemical or physical in nature, is to 

 compare its temperature coefficient with the temperature coeffi- 

 cients of various known physical or chemical phenomena. In 

 this way it has been shown that the rates of increase of the heart 

 beat, conduction of the nerve impulse and many other organic 

 processes are due to chemical processes since they are accelerated 

 to the same degree by a rise of temperature as is the velocity of 

 chemical reaction. The latter are distinguished from the great 

 majority of physical processes, in that they are affected enor- 

 mously by a rise in temperature. Chemical reactions proceed 

 two to three times more rapidly with every io° rise in tempera- 

 ture. The same method may be used to see whether the action 

 of a given substance is chemical or physical in nature. 



My object in studying the effectiveness of acetic acid at dif- 

 ferent temperatures was primarily to test Loeb's hypothesis, that 

 the reason the fatty acids are the most efficient acids in calling 

 forth membrane formation is because of their property of dis- 

 solving lecithin and other lipoids. Solution is a physical process. 

 The solubilities of most substances are not greatly affected by 

 temperature. Unfortunately the exceptions to the above rule 

 are mostly exhibited by fatty substances. As nothing is known 

 of the solubility of lecithin in acetic acid at different temperatures, 

 a definite answer as to the action of acetic acid on the eggs cannot 

 be given. Certain other possible actions, however, are excluded 

 and certain others included by my results. These will be dis- 

 cussed after giving the results. 



