564 



SCIENCE 



[N. S. Vol. XXXVI. No. 930 



Three methods have been used singly and 

 in various combinations in this study. By 

 the plasmolytic method a separation of the 

 hyaline plasma-layer from the vitelline mem- 

 brane is easily afiected. Vital staining dif- 

 ferentiates clearly the various structures on 

 the surface of the egg. Janus Green (di- 

 methylsafraninazodimethylanalin) in dilute 

 solutions stains the egg-jelly light blue. It is 

 also beautifully demonstrated by a number of 

 other vital stains. In concentrated solutions 

 of janus green the jelly shrinks to a mere 

 hull. Slightly concentrated solutions of 

 isamin blue, dissolved in sea water by boiling, 

 stain the svpollen vitelline membrane a deep 

 blue while the hyaline layer is much lighter 

 in color. Toluidin blue stains the hyaline 

 layer of the cytoplasm and the vitelline mem- 

 brane, but as a differential stain it does not 

 equal isamin blue. 



The removal of the egg- jelly and vitelline 

 membrane from the fertilized and unfertilized 

 eggs was affected by dissection with glass 

 needles made from very hard Jena glass 

 tubing about 5 mm. in diameter. The points 

 on many of these needles measured less than 

 one half micron. The needles were held in a 

 Barber pipette-holder and the dissections 

 made under a magnification of five hundred 

 and sixty- two diameters. 



It seems that the type of reaction described 

 for the egg of Ariacia is a somewhat common 

 one, since essentially the same changes occur 

 in the eggs of Chcetopterus and the moUusk 

 Oumingia. In these two forms the maximum 

 swelling of the vitelline membrane does not 

 occur until about twenty to thirty minutes 

 after insemination of the eggs. 



An analysis of the reaction of the egg of 

 Arbacia to the spermatozoon has been at- 

 tempted. Puncture of the vitelline membrane 

 has failed to produce the reaction. Doses of 

 from one to five spermatozoa have been injected 

 into the egg-jelly and the relation between the 

 time required for the penetration of the vitel- 

 line membrane by the spermatozoon and the 

 extent and location of the swelling of this 

 structure have been studied. By injecting 



spermatozoa into the egg-jelly, in a small per- 

 centage of cases a single spermatozoon be- 

 comes attached to the vitelline membrane and 

 produces the reaction that has been described. 

 The passage of the spermatozoon through the 

 vitelline membrane has been observed in a 

 number of eggs. It has been found possible 

 to remove the spermatozoon from the vitelline 

 membrane after it has caused the reaction. 

 The real difiiculty in this type of experiment 

 is not the size of the spermatozoon, but the 

 fact that when even four or five spermatozoa 

 are injected into the egg-jelly they usually 

 swim out and away from the egg. This neces- 

 sitates the making of many injections in 

 order to get a single spermatozoon to attach 

 itself to the vitelline membrane and start the 

 reaction. 



As far as my evidence goes at the present 

 time it seems that the primary function of the 

 much discussed reaction of the egg of Arbacia 

 to the spermatozoon is the prevention of poly- 

 spermy. 



The details of this study will appear later. 



G. L. Kite 



The Marine Biological Laboeatoky, 

 Woods Hole, Mass., 

 September 7, 1912 



A SIMPLE METHOD OF MAKING AETIFICIAL CELLS 



RESEMBLING SEA URCHIN EGGS IN CERTAIN 



OP THEIR PHYSICAL PROPERTIES 



Several years ago Eobertson showed that if 

 chloroform was shaken with egg-albumen solu- 

 tion, the droplets would not reunite even when 

 washed in water, because of the formation of 

 a proteid film on the chloroform surface. It 

 can be readily observed that such droplets 

 shrink in volume, owing to the passage of 

 chloroform into the water outside. 



While studying the penetration of alkalies 

 into lecithin in various solvents, I noticed 

 that if lecithin is dissolved in chloroform and 

 the solution shaken with proteid solutions, the 

 chloroform of the resultant globules is in time 

 completely replaced by water. Eventually, 

 then, instead of lecithin in chloroform, we may 

 obtain small cells of lecithin in water sur- 



