626 STUDIES IN GENEKAL PHYSIOLOGY 



searching the control material for segmented eggs, but were 

 never able to find a single one. 



In addition to these control experiments we made several 

 others. It was necessary to apply the mixture of equal parts 

 of the 2 -n MgCl 3 solution and sea-water for from one to 

 two hours to bring about the development of the unfertilized 

 eggs. We made it a rule to take out one portion of eggs 

 from this solution much earlier in some cases after ten min- 

 utes. In no case did one of these eggs segment or develop. 



A third series of control experiments was applied. Solu- 

 tions with less MgClg and more sea-water were tried. In 

 solutions of 30 c.c. 2 ^n MgCl 2 , and 70 c.c. sea-water not an 

 egg was able to develop. 



If the first animal opened in these experiments happened 

 to be a male, the instruments were at once laid aside for 

 disinfection, and the next animal was opened by another 

 experimenter with the same precautions. 



In some experiments we used sea-water that had been 

 filtered through a new Pasteur filter. Although no sperma- 

 tozoa are able to pass through such a filter, the eggs treated 

 with a mixture of equal parts of a 2 -/n MgCl 3 solution and 

 filtered sea- water developed, while none of the control eggs 

 were able to develop. 



In one of the former papers I mentioned the fact that 

 the mixture used for artificial fertilization killed the sperma- 

 tozoa in a comparatively short time and injured many of 

 the eggs. Contrary to the common prejudice, it is a fact 

 that spermatozoa are much more sensitive and are killed 

 much sooner than the egg. 



My experiments at Pacific Grove were carried on with 

 Strongylocentrotus franc iscanus and S. purpuratus. In both 

 animals artificial parthenogenesis can easily be accomplished. 



In the experiments at Pacific Grove I enjoyed the valu- 

 able assistance of Mr. W. E. Garrey. 



