258 STUDIES IN GENEEAL PHYSIOLOGY 



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 segmentation of the protoplasm. 

 Eggs which had been impregnated in normal sea-water were 

 brought into the concentrated solution and watched care- 

 fully. No segmentation of the protoplasm took place ; but 

 the nucleus divided, indeed, into two, and then further divi- 

 sions followed. I tried, moreover, to see whether the proto- 

 plasm of such eggs, if brought back into normal sea-water, 

 divided into as many cleavage spheres as there were nuclei 

 preformed. I saw, indeed, that every nucleus becomes the 

 center of one of these projections, which later on become 

 cleavage spheres. Dr. Conklin was kind enough to stain 

 some of the eggs which had been in the concentrated solu- 

 tion for some time and which showed no trace of segmenta- 

 tion. Some of these stained eggs showed very distinctly from 

 four to about thirty distinct nuclei. In other eggs the seg- 

 mentation 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 

 polyspermia 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 egg; or from the 

 conjugated nuclei, as in the normal case ; or from both conju- 

 gated nuclei and male pronuclei together, as in some cases 



