No. 2.] PHYSIOLOGICAL MORPHOLOGY. 257 



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 

 of these experiments. But the following fact may be of inter- 

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

 there until they were all in the two-cell stage. Then I brought 

 them into the concentrated solution. The cleavage stopped 

 directly. After having been there for three hours, I brought 

 them back into normal sea-water ; and now every cleavage 

 sphere divided at once into more than two pieces, sometimes 

 into eight or even more. 



5. I concluded from the foregoing experiments that in the 

 concentrated solution a segmentation of the nuclei might take 

 place without any segme?itatio7i of the protoplasm. Eggs 

 which had been impregnated in normal sea-water were brought 

 into the concentrated solution and watched carefully. No 

 segmentation of the protoplasm took place ; but the nucleus 

 divided, indeed, into two, and then further divisions followed. 

 I tried, moreover, to see whether the protoplasm of such eggs, 

 if brought back into normal sea-water, divided into as many 

 cleavage spheres as there were nuclei pre-formed. I saw, 

 indeed, that every nucleus becomes the centre of one of these 

 projections, which later on become cleavage spheres. Dr. Conk- 

 lin was kind enough to stain some of the eggs which had been 

 in the concentrated solution for some time and which showed 

 no trace of segmentation. Some of these stained eggs showed 

 very distinctly from four to about thirty distinct nuclei. In 

 other eggs the segmentation of the nucleus was not so perfect. 

 The nucleus, extremely enlarged, seemed to consist of several 

 parts which, however, were still connected. These eggs had 

 been killed at a time when the eggs of the same lot which had 

 remained in normal sea-water all the time were in about the 

 sixty-four-cell stage. 



6. Fol and O. and R. Hertwig found that in the case of poly- 

 spermia the egg at once divides into about as many cells as 

 there are asters. We know that for the segmentation of the 

 protoplasm it does not make any difference whether the nuclei 

 are derived from the male pronuclei exclusively, as in the case 

 of the impregnation of an enucleated ^gg, or from the conju- 



