EXPERIMENTS ON CLEAVAGE 



lot, just as in the foregoing lots of the same kind, 1 found 

 cleavage spheres of very ditl'erent sixes in the same egg. At 

 <> :-")() 1 repeated the same experiment, taking out a lot of 

 eggs from the eoncentrated solution, and bringing them hack 

 into normal sea-water. Not one egg showed any trace of 

 segmentation, but in a very short time about twenty min- 

 utes the eggs segmented at once into a great number of 

 small cleavage spheres, the smallest and most numerous having 

 tlu 1 size of a cleavage sphere of about the sixty-four-cell stage. 

 I repeated this experiment about twenty times, always with 

 the same result, which in a few words may be expressed as 

 follows: If ico bring impregiKded eggs info sea-irater of a 

 certain higher concentration, no segmentation takes place; 

 hut if /re bring them back info normal sea-water, theydiride 

 in about In-cut // minutes directly into 'nearly, but not <]/tile, 

 so many clearage spheres as they irould contain l>y that 

 time if they had remained in normal sea-water all the time. 

 It must be added, however, that the normal eggs in this 

 experiment are always ahead of the plasmolyzed eggs in 

 regard to their stage of segmentation, and that their advance 

 becomes the more obvious the farther they develop. 



Eggs, after having been in the concentrated solution from 

 twelve to twenty-four hours, do not segment at all if brought 

 back into common sea- water. All these experiments are the 

 more satisfactory the better the material is. 



4. I varied these experiments by sometimes bringing the 

 impregnated eggs into the concentrated solution immediately 

 after impregnation, and sometimes later. The result remained 

 the same, on the whole, and I will not dwell upon the details 

 if these experiments. But the following fact may l>e of inter- 

 est : I impregnated eggs in normal sea-water, and left them 

 then- until 'hey were all in the two-cell stage. Then I 

 brought them into the concentrated solution. The cleavage 

 ^topped directly. After having been there for three hours, 



