730 STUDIES IN GENERAL PHYSIOLOGY 



alive for several days until they finally become the prey of 

 bacteria; while the mature eggs become opaque and die in 

 from four to twelve hours after maturation has been com- 

 pleted. 



Is the death of the mature but undeveloped egg brought 

 about through internal conditions, or through the bacteria 

 contained in the sea-water? 



A trustworthy way of determining this consists in making 

 sterile culture of the eggs in sea-water. This is a relatively 

 simple procedure in the case of starfish. Eight flasks were 

 sterilized, filled with sterilized sea-water, and again heated 

 for twenty minutes on three successive days to 100 C. A 

 female starfish was thoroughly washed externally, an arm 

 was opened, and one of the ovaries removed with sterilized 

 forceps and placed in sterilized sea-water. From the thick 

 stream of eggs which at once flowed out of the ovary, a few 

 drops were quickly introduced with a sterilized pipette into 

 each of the sterilized flasks. A second series of eight flasks 

 contained normal, unsterilized sea- water, and a few drops of the 

 same eggs were introduced into these flasks also. A third series 

 of flasks were filled with sea-water, to each of which were 

 added 2 c.c. of a putrid, foul-smelling culture of old starfish 

 eggs in order to bring about a rapid development of bacteria 

 from the beginning. Each of these flasks also contained 

 eggs from the same culture as those in the sterilized flasks. 



That perfect sterilization had been attained in the first 

 eight flasks was proved by the fact that all the flasks remained 

 absolutely clear and cloudless during the course of the experi- 

 ment, and that three of the flasks which had not been opened 

 are even today (after six weeks) absolutely clear, and every 

 egg can be individually recognized. The flasks containing 

 the unsterilized sea-water became cloudy within as short a 

 time as twenty -four hours, and after two days the eggs had 

 become the prey of bacteria and no individual egg could be 



