de;partmsnt of marine biology. 131 



The rate at which nerve-conduction decreased in velocity in MgCla and 

 CH3COOH was also studied to determine if it followed a logarithmic curve, 

 which would be the case if the hypothetical Mg-proteid or acid-proteid re- 

 action was a monomolecular reaction following the law of mass action. As 

 yet I have not had time to study the data. A comparison was also made of 

 toxic concentrations of CH3COOH and HCL. 



(2) The Chemical Action of CHsCOOH in Causing Artificial Membrane Formation in 

 Sea-urchin Eggs with Further Experiments on Membrane Formation. 



In order to test Loeb's hypothesis that the reason the fatty acids only cause 

 membrane formation in sea-urchin's eggs is because they dissolve out the 

 lipoids, the efficiency of acetic acid at different temperatures was tried. It 

 was found that the time required for the acid to exert its effect was about 

 doubled for every 10° lowering of temperature. 



The recent work of Delage* on electric parthenogenesis has made pos- 

 sible an exact comparison of the methods of stimulating contractile tissues 

 (muscles and sensitive plants) and the methods of causing artificial parthen- 

 ogenesis in various eggs. The various means of stimulating muscles may be 

 roughly classified as electrical, mechanical, thermal, chemical, and osmotic, 

 and these are exactly the heads under which the various means of exciting 

 eggs to develop may be arranged. In a series of recent papers,f R. S. Lillie 

 has shown that the essential effect of stimulation in contractile tissues is an 

 increase in permeability of the plasma membrane, this change allowing the 

 escape of the reaction-products of the reaction on which the energy trans- 

 formations in contraction depend. This permits the reaction to proceed dur- 

 ing contraction, until it is again checked by a second accumulation of reaction- 

 products during rest. Regarding the egg as a system of reacting substances, 

 one would expect these to come to equilibrium at one point in their cycle. 

 This equilibrium is upset, and development proceeds by an increase in per- 

 meability of the egg-membrane allowing the exit of some reaction-product 

 (possibly C02, as in the case of muscle). Normally, this is brought about by 

 the entrance of a spermatozoon artificially by the various parthenogenetic 

 agents. The recent work of Loeb has shown that many of the substances 

 which cause parthenogenesis are hasmolytic substances, increasing the per- 

 meability of blood-corpuscles to such a degree that the haemoglobin escapes. 



With the above idea in mind, a study was made of the process of mem- 

 brane formation as being the first marked change in the egg after fertilization. 

 Since the egg of the sea-urchin, about six hours after shedding, can be fertil- 

 ized with foreign sperm, it was thought that the change undergone on stand- 

 ing might possibly be in the direction of increased permeability. Such did 

 not prove to be the case, as it was found that a very slightly longer treatment 

 with CH3COOH was necessary to produce membranes in eggs which had 

 stood for six hours. If the egg does undergo no change in the direction of 

 increased permeability on standing, this may be connected with the fact that 

 sea-urchin eggs do not develop spontaneously as readily upon standing as do 

 some other eggs. 



The process of membrane formation may be divided into two phases, the 

 actual membrane formation and the separation of the membrane from the 



* Archiv. de zool. exp. et Gen., 1908. Notes et Revue, p. xxx. 

 t Especially Am. J. Phys., vol. 24, 1909, pp. 14 to 44. 



