April 20, 1900.] 



SCIENCE. 



613 



a temperature of from 50 to 70° C. and was 

 kept at that temperature for about ten 

 minutes and allowed to cool very slowly. 

 The control experiments proved that, as 

 was to be expected, the spermatozoa are 

 killed by this treatment. During the time 

 the water was heated no sea urchin was 

 opened in the laboratory or was even 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 sur- 

 gical 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 sec- 

 tion 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 part of the eggs was put into steril- 

 ized sea water to serve as control material. 



A second portion was put into a mixture of 

 equal parts of sterilized sea water and a 

 20/8 n MgClj 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 blastulae and swam 

 around the next day, not an egg of the con- 

 trol material even segmented. "We spent 

 hours 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 

 20/8 n MgCIj solution and sea water for 

 from one to two hours in order 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 minutes. In 

 no case did one of these eggs segment or 

 develop. 



A third series of control experiments was 

 applied. Solutions with less MgClj and 

 more sea water were tried. In solutions of 

 30 cc. 20/8 n MgCl^ and 70 cc. sea water not 

 an egg was able to develop. 



If the first animal opened in these ex- 

 periments happened to be a male the in- 

 struments were at once laid aside for disin- 

 fection and the next animal was opened by 

 another experimenter with the same pre- 

 cautions. 



In some experiments we used sea water 

 that had been filtered through a new Pas- 

 teur filter. Although no spermatozoa are 

 able to pass through such a filter, the eggs 

 treated with a mixture of equal parts of a 

 20/8 n MgCl^ 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 spermatozoa in a 

 comparatively short time and injured many 



