1 66 T. H. Morgan. 



the serum of the normal rabbit already contains a substance that 

 has a powerful antitoxic action on the poison of the starfish, so 

 that it was not necessary to obtain an antitoxin by injecting the 

 poison into the rabbit. The antitoxin of the rabbit's serum was 

 added to water containing the eggs of Asterias, and then sperm 

 from a sea-urchin was supplied. Von Dungern often obtained 

 two- and four-cell stages in this way, but the results were uncertain, 

 and he could not decide whether fertilization had or had not 

 taken place. It seems not improbable, I think, that the outcome 

 may have been due to artificial parthenogenesis which occurs 

 very readily in the eggs of certain starfish; in fact, it is very 

 difficult to prevent its occurrence, unless the eggs are very care- 

 fully handled. 



The same poison that is present in the eggs of the starfish is 

 also secreted by the skin. It is also rendered harmless by the 

 rabbit's serum. In the sea-urchin there is a poisonous substance 

 in the gemmiform pedicellariae, which is very injurious to the 

 sperm of the starfish. If lOO of the pedicellariae of Sphaerechi- 

 nus are rubbed up in one ccm of sea-water, the solution will de- 

 stroy in a quarter of an hour the sperm contained in ten to tw^enty 

 litres of sea-water. The minimal lethal dose for 2 ccm is 1/5 120 

 to 1/ 1 6240 ccm. The spermatozoa of Sphaerechinus itself are 

 killed by this fluid, but a much stronger dose is necessary. On 

 the other hand an extract of the egg of Echinus, Sphaerechinus, 

 Strongylocentrotus, or Arbacia does not kill the spermatozoa of 

 the starfish even in the strongest solutions. What then prevents 

 the spermatozoa of the starfish from entering the eggs of these 

 sea-urchins? There Is another factor. Von Dungern thinks, that 

 interferes with this combination. The egg membrane of these 

 urchins has an agglutinizing effect on the spermatozoa of the 

 starfish. This agglutinizing effect appears to be the same phe- 

 nomenon as that seen "whenever cells of any kind are introduced 

 into the body of another animal." So far as this process is in- 

 volved in the union of germ-cells. Von Dungern thinks that under 

 certain conditions it might assist the fusion, while under others 

 it might interfere with it. Thus two naked and equivalent cells 

 might be helped to unite, while an egg surrounded by an agglu- 



