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 foto 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 *,!n 
MgCl, 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 blastule and swam around the next day, not an egg of 
the control material even segmented. We spent hours: 
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