Februaey 2, 1900.] 



SCIENCE. 



179 



that of the former. Saturated solutions 

 were used. The eggs divide usually into a 

 larger and a smaller part and the segmen- 

 tation may continue through several subse- 

 quent divisions. The result is the same 

 whether the eggs are left in the solution or 

 whether transferred after two to three 

 hours to sea water. 



A certain time is necessary to start these 

 changes in the eggs. Eggs left for one hour 

 in the solution showed little subsequent 

 segmentation, and even after one and a-half 

 hours sojourn in the solution, only a few of 

 the eggs divided after being returned to sea 

 water. Richard Hertwig had shown that 

 if the unfertilized eggs of a sea-urchin are 

 put into sea water containing strychnine, 

 that after a time the nuclear wall breaks 

 down, a nuclear spindle forms around the 

 chromosomes, and after division of the lat- 

 ter, a new nucleus reforms. My own re- 

 Bults show that a nearly similar change 

 takes place in Arhacia, but the chromosomes 

 of many eggs separate after division and 

 make two (or more) new nuclei. If this 

 happens, a subsequent division of the pro- 

 toplasm takes place. 



Ttie changes brought about by the strych- 

 nine have many points of resemblance to 

 those that take place in the unfertilized 

 eggs acted upon by certain salt solutions : 

 magnesium, sodium or potassium chloride. 

 In the latter instances I have tried to show 

 that the transportation of the chromosomes 

 is brought about by the astrospheres that 

 appear in the egg and the number of new 

 cells that form is, in general, in proportion 

 to the number of astrospheres that are 

 present in the egg. The latter being more 

 numerous, produce a wider distribution of 

 the chromosomes. 



The absence of these astrospheres in the 

 eggs acted upon by the strychnine accounts 

 for the fewer divisions of the protoplasm in 

 these eggs. All of these substances pro- 

 duce a slight shrinkage of the egg and it 



seemed not improbable that the cleavage 

 of the egg might be the result of the plas- 

 molysis, especially since the fertilized egg 

 also sets free water or some other fluid at 

 the moment the spermatozoon enters. In 

 order to test this possibility I tried the 

 effect of different strengths of magnesium 

 and sodium chlorides — percentages ranging 

 from those that do not affect the eggs to 

 those that kill the eggs in a few minutes. 

 The results show that isotonic solutions of 

 these two salts produce very different re- 

 sults. The eggs will withstand a solution 

 of magnesium chloride that was twice the 

 strength of sodium chloride. This is the 

 more surprising since the latter salt exists 

 in sea-water in nearly ten times the quantity 

 of the former. 



The results also show that it takes a 

 weak solution very much longer to act 

 than a stronger one. The length of time 

 being out of all proportion to the plasmo- 

 lyzing effect of the solution. Further, a 

 solution so strong that it will kill the eggs 

 in half an hour, will cause the eggs to di- 

 vide in several parts if they are left in the 

 solution for five minutes and then trans- 

 ferred to sea- water. 



In a previous paper I have compared the 

 action of these substances to the action of 

 stimuli on a nerve or a muscle. A large 

 number of very different kinds of stimuli 

 will start a nerve-impulse or a muscular 

 contraction, the result depending more upon 

 the structure of the living part than upon 

 the stimulus employed. The unfertilized 

 egg of the sea-urchin is likewise in a state 

 of unstable equilibrium prepared to undergo 

 a definite series of changes along given 

 lines. These changes can be started in 

 several ways, and resemble more or less 

 perfectly the changes following fertilization, 

 but I believe it would be as erroneous to 

 compare the action of these substances di- 

 rectly with the process of fertilization as it 

 would be to affirm that the action of a 



