184 The Structure of Protoplasm 



has learned to recognize them they can be detected in the neighbor- 

 hood of every thin area as grayish areas surrounded by the small 

 granule-containing vacuoles, with a darker gray nucleolar center. 

 They are much larger than the granule-containing vacuoles. A flake 

 of iodine placed under "the cover glass soon reveals great numbers 

 of nuclei and also a diffuse port-wine color in the protoplasm indi- 

 cating the presence of glycogen. 



VISCOSITY OF SLIME MOLD 



The following quotation from Camp expresses in general terms 

 rather obvious conclusions that one would reach from observations 

 and testings with a needle: (p. 372), "All of those considerations 

 would seem to lead to the conclusion that the viscosity of the 

 protoplasm of a plasmodium varies from place to place in the Plas- 

 modium, that it changes with changing external and internal condi- 

 tions, and that alterations in the physical state, i. e., changes from 

 sol to gel and gel to sol, take place more or less constantly through- 

 out all parts of a plasmodium. Normally, therefore, the protoplasm 

 of Plasmodia does not have an absolute and unchanging viscosity, 

 and variations in its viscosity seem to be due to alterations in the 

 physical state of the hyaloplasm." 



Perhaps the presence of great numbers of small vacuoles, mito- 

 chondria, and nuclei and the relatively small amount of hyaloplasm 

 may have something to do with the apparent ease with which the 

 protoplasm or hyaloplasm changes from sol to gel and gel to sol. 



CELL DIVISION— MITOSIS 



Cell division consists of a series of interdependent reactions 

 which lead to a series of overlapping events, each of which takes 

 a considerable period of time. Most, if not all, of the visible reactions 

 are due to viscosity changes. The reactions lead to two essential 

 events, the formation of the daughter nuclei and the cleavage of 

 the cell into two parts. 



Mitotic division of the nucleus is not always accompanied by cell 

 cleavage so that perhaps none of the events which result in cell 

 cleavage are necessary for mitotic division of the nucleus. The 

 events, however, which lead to cell cleavage or at least some of 

 them are probably dependent upon events which result in the mitotic 

 division of the nucleus. 



A brief outline of the events as exhibited by an ordinary living 

 fibroblast in tissue culture is as follows: 



