640 ORGANS OF GENERATION. 



normal larvae. The principal points in the treatment of such eggs are 

 the following. 



The formation of the fertilization membrane can be brought about 

 by placing the eggs in sea water which has been faintly acidified with 

 a fatty acid, for example with butyric acid, and after 1J to 2 minutes 

 placed again in sea-water. The formation of the membrane now takes 

 place. The oxyacids and especially the inorganic acids are less active, 

 than the fatty acids. The H-ions are without effect in this acid action 

 and LOEB explains the action by the introduction of the undissociated 

 molecules into the egg. Parallel with the membrane formation chemical 

 processes begin, among which we must especially mention oxidations. 

 These processes, if they proceed undisturbed, especially at 15 or above, 

 lead quickly to the death of the egg. This can, nevertheless, be prevented 

 if the oxidation processes are inhibited 40-60 minutes after the mem- 

 brane formation by removing the oxygen or by the addition of some 

 potassium cyanide. In this process probably certain injurious substances 

 for the egg are destroyed. If eggs treated in this way are placed in 

 sea-water after 2-3 hours they develop in a normal manner. 



The membrane formation can also be brought about in other ways 

 besides by the action of acids, for example by treating the egg with saponin, 

 solanin, digitalin, soaps and fat dissolving substances such as amylene, 

 benzene, toluene, chloroform, ether and alcohol. The sea-urchin egg is 

 also excited to membrane formation by the serum of certain animals. 

 Alkalies and elevation of temperature can also cause the formation of 

 membrane. 



On the other hand the chemical processes, which, when not prevented, 

 lead to the death of the egg, can also be inhibited by placing the eggs in 

 a hypertonic solution (50 cc. sea-water and 8 cc. 2.5 normal NaCl) 

 about one hour after the artificial membrane has been formed and then 

 after 20-50 minutes placing them in sea-water again. 



According to LOEB the artificial fertilization of the sea-urchin's egg 

 depends upon two special actions, of which the first brings about the for- 

 mation of membrane with oxidation processes by means of cytolysis 

 while the second gives the direction of these oxidation processes necessary 

 for the maintenance of life. 



The non-fertilized, ripe egg, as the investigations of LOEB on star- 

 fish have shown, dies in 4-6 hours at sufficiently high temperatures. The 

 death of the egg can, nevertheless, be prevented if oxygen is removed 

 from the egg or the oxidation inhibited by the addition of traces of potas- 

 sium cyanide. If the ripe egg is fertilized by spermatozoa then it remains 

 alive although the process of fertilization, as WARBURG 1 found, causes 



1 Zeitschr. f. physiol. Chem., 57, 60, 66. 



