ARTIFICIAL PARTHENOGENESIS 625 



kept there. The sterilized sea-water was kept in special 

 flasks and covered jars which were utilized for this purpose 

 only. Before we started an experiment we disinfected our 

 hands thoroughly with soap and brush in the same way as is 

 customary in a surgical operation. Every sea-urchin before 

 it was opened was exposed for from two to five minutes to a 

 powerful stream of fresh water, and care was taken to wash 

 the whole surface of the animal as thoroughly as possible 

 with fresh water. The mouth of the sea-urchin was then 

 cut out with scissors that had been sterilized the day before 

 in the flame and had been kept dry since. Through the 

 excision of the mouth the sexual glands were exposed, and 

 their color allowed to decide whether the animal was a male 

 or a female. If the first animal that was opened was a 

 female, the intestine was removed with a sterilized forceps, 

 and care was taken not to bring the forceps in contact with 

 the ovaries or with the outside surface of the animal. After 

 the intestine had been removed and nothing left except the 

 ovaries, the inside of the animal was repeatedly filled with 

 fresh water and washed out. Then each of the five ovaries 

 were taken out in toto with a sterilized section lifter, and 

 special pains were taken that the ovaries did not come in 

 contact with the surface of the sea-urchin or with the hands 

 of the experimenter. The ovaries were first put into a dish 

 of fresh water, were washed off carefully, and then put into 

 sterilized sea-water. 



One portion of the eggs was put into sterilized sea-water 

 to serve as control material. A second portion was put into 

 a mixture of equal parts of sterilized sea-water and a 2 n 

 MgCl 2 solution. An hour or two later these eggs were 

 taken out of this mixture and put into sterilized sea- water- 

 While of the latter eggs as many as 25 per cent, developed 

 into blastulpe and swam around the next day, not an egg of 

 the control material even segmented. We spent hours 



