172 DYNAMICS OF LIVING MATTER 



tific tone, and if his precautions against sources of error were more 

 adequate. Still, it is not impossible that some physical or chemical 

 condition accidentally present in Algiers may bring about effects 

 similar to the extraction of water from the eggs of these animals in this 

 country. 



Since it is' possible to fertilize the egg of the sea urchin and that of 

 the starfish by the spermatozoa of the latter species, it seemed also pos- 

 sible that the fertilization of the starfish's egg might be caused by the 

 same substances which cause the f ertihzation of the egg of the sea urchin. 

 I have made experiments on the egg of a form of Asterina which is com- 

 mon in the bay of Monterey.* This egg forms a membrane upon the en- 

 trance of a spermatozoon. I found that as in the case of the sea-urchin 

 egg, the egg of Asterina forms a membrane after having been treated with 

 a fatty acid. The only difference is that the egg of Asterina requires more 

 acid for this result, than the egg of Strongylocentrotus. When the eggs of 

 Asterina had been put for about one and one half to two minutes into a 



mixture of 50 c.c. sea water + 5 c.c. — acetic or butyric acid, they 



formed a membrane when put back into normal sea water. When they 

 were put into 50 c.c. sea water -I- i c.c. benzol or amylene, they formed 

 a membrane while they were in this mixture. 



Eggs in which this membrane formation had been called forth were 

 able to develop into normal larvae, and the development of such eggs 

 resembled in rapidity and the form of the larvse completely that pro- 

 duced by sperm. 



The egg of the starfish is, as a rule, not mature when it leaves the 

 ovary. It possesses a large nucleus, and the process of maturation con- 

 sists in the nucleus being dissolved in the protoplasm of the egg and the 

 polar bodies being thrown out. As long as the large nucleus is visible 

 in the egg it cannot be fertih'zed by a spermatozoon, nor can its develop- 

 ment be called forth by a treatment with one of the fatty acids or with 

 one of the hydrocarbons, like benzol or amylene. Not until the nucleus 

 has become dissolved in the protoplasm can a spermatozoon fertilize the 

 egg, and at about the same time it becomes possible to produce artifi- 

 cially a membrane formation and development. 



There is a noticeable difference in the method by which the starfish egg 

 can be caused to develop and the method which is necessary in the case 

 of the sea-urchin egg. For the former the process of artificial mem- 

 brane formation is sufficient, while the sea-urchin egg has, in addition, 

 to be submitted for a short time to the action of hypertonic sea water. 

 This difference is rendered a little more comprehensible by the fact that 

 * Loeb, University of California Publications, Physiology, Vol. 2, p. 147, 1905. 



