Febbuart 26, 1904.] 



SCIENCE. 



351 



expressions of different physiological states. 

 As a means of gaining further insight into the 

 physiological conditions underlying cleavage, 

 I adopted the plan two years ago of testing 

 the susceptibility of the egg at diiierent stages 

 in the first cleavage. Pptassium cyanide was 

 used; also lack of oxygen produced by a cur- 

 rent of hydrogen. A rhythm of alternate 

 susceptibility and resistance was demonstrated. 

 About ten or fifteen minutes after fertilization 

 the echinoderm egg is very easily poisoned 

 by KClSr. The resistance increases from that 

 time to about the time of the first cleavage. 

 A period of susceptibility follows; then an- 

 other rise of resistance as the second cleavage 

 approaches. Probably this rhythm goes on in 

 each subsequent division. The rhythm to lack 

 of oxygen is similar. This makes it probable 

 that the cell needs oxygen, especially in the 

 period immediately following division, this 

 being the time of nuclear growth and presum- 

 ably of active synthesis. 



During the last summer I have been work- 

 ing on the effects of heat and cold on the divid- 

 ing egg. The experiments show well-marked 

 rhythms of susceptibility and resistance dur- 

 ing each cleavage. The details will be pub- 

 lished later. 



While pursuing this work it occurred to me 

 that the production of 00^ during cell division 

 might also run in rhythms. The question 

 Beemed one of sufficient interest to warrant 

 a careful investigation. Unfortunately ap- 

 paratus for accurate chemical analysis was 

 not available at Woods Hole. Furthermore, 

 the season had so far advanced that only com- 

 paratively small quantities of Ariacia eggs 



were obtainable. It seems best, therefore, to 

 put my results in the form of a preliminary 

 piiblication, it being understood that the con- 

 clusions are tentative and subject to revision 

 on further experimentation. 



The apparatus finally adopted is shown in 

 the diagram. Positive pressure forced air in 

 the direction of the arrows. The test-tubes 

 were tightly closed with rubber stoppers. 

 Ttibes A and B contained KOH solution to 

 absorb the CO, of the air. Tube C contained 

 Ba(OH), solution and served as an indicator 

 of the efficient action of A and B. D con- 

 tained Ariacia sperm in sea water. E con- 

 tained the unfertilized eggs of a large number 

 of feraales, in sea water. These eggs had been 

 carefully freed from body liquids and from 

 immature ova by allowing them several times 

 to sink through sterile, filtered sea water in 

 test-tubes or Naples jars. Tube E was kept 

 at a constant temperature, usually 23°. Tubes 

 F and O contained Ba(OH)„ solution whose 

 degree of turbidity constituted an index of 

 the amount of CO, produced by the eggs and 

 sperm. 



Before the experiment began the egg tube 

 was nearly filled with sterile sea water and a 

 current of air free from CO, passed through 

 for several hours. Tube D, which meanwhile 

 had been empty, now received a few cubic 

 centimeters of sea water containing fresh 

 sperm. The eggs, recently washed, were added 

 (with as little water as possible) to the water 

 in E. The air was allowed to pass for fifteen 

 or twenty minutes. Then measured amounts 

 of Ba(OIT), solution were placed in F and O, 

 the air current being continued. After ten 

 minutes the eggs were fertilized and fresh 

 tubes substituted for F and G, the first two 

 being securely closed with rubber stoppers and 

 labelled ' 0.' Every ten minutes fresh tubes 

 were substituted at F and O, those used dur- 

 ing the ten minutes following fertilization 

 being numbered ' 1,' and so on. 



It was found that in ten minutes either be- 

 fore or after fertilization tube F became 

 visibly turbid. On standing, a precipitate of 

 BaC03 formed. Tube G showed little or no 

 turbidity or precipitate and, therefore, was 

 usually disregarded. In some experiments 



