Behavio}^ of the Germ-cells 1 79 



Buller's experiments with the eggs of sea urchins and starfish 

 have given important results. He pointed out that spermatozoa 

 accumulate around immature eggs, and also around mature eggs 

 that had been killed in osmic acid and then thoroughly washed 

 in sea water. In this case it is highly improbable that any attrac- 

 tion could exist. The results are due to those spermatozoa that 

 accidentally run into the membrane of the egg, remaining stick- 

 ing there as a result of some physical property of the jelly or of 

 some reaction on the part of the spermatozoon. BuUer showed 

 by means of the following experiment that the eggs do not se- 

 crete an attracting substance. Eggs were allowed to stand in a 

 little water from two to twelve hours. Capillary tubes were then 

 filled with this water and placed in a drop of sea water containing 

 the sperm. No collecting of spermatozoa around the ends of the 

 tube was observed. He alse tried other substances in the tubes, 

 viz. salts, sugars, ferments, and alcohol, etc., but no evidence 

 of their action in attracting the spermatozoa was observed. 



Buller thinks that the spermatozoa are sensitive to contact, 

 hence on coming into contact with the membrane bore into it. 

 The spermatozoa swim in spirals in the water, but on entering 

 the jelly they take a straight course, which in most cases will 

 bring them into contact with the egg, although, if they should 

 enter quite obhquely they may bore through the periphery of the 

 membrane and pass out again on the other side. Thus even 

 after entering the membrane, there is no evidence that the egg 

 attracts the spermatozoa toward itself. 



On the other hand it has been shown by von Dungern that the 

 egg and its membranes may contain and even give off substances 

 that act in some cases injuriously on the spermatozoa of other 

 species. The egg of the starfish, Asterias glacialis, contains a 

 substance that acts as a poison on the spermatozoa of the sea 

 urchins — Echinus or Sphasrechinus. The minimal lethal dose 

 for sperm mixed with two cubic centimeters of sea water varies 

 with different individuals between the limits of -g^Q to eioo" 

 parts for half an hour. The same poison is found also in the skin 

 of the starfish. Cross- fertihzation of the eggs of this starfish by 



