THE BIOLOGY OF THE CELL SURFACE 



of it goes to make up new nuclei and another portion forms 

 the new cell-boundaries. Thus, the viscosity of the cyto- 

 plasm, for example, in the individual blastomere can not be 

 the same as that of the cytoplasm of the uncleaved egg. 

 Furthermore, the diflferential distribution of the cytoplas- 

 mic inclusions during cleavage certainly alters the original 

 physical state of the egg. 



With subdivision of the egg into blastomeres, changes in 

 the chemical reactions take place. Each blastomere repre- 

 sents a separate reaction-chamber of capillary dimensions 

 favoring especially those reactions which are confined to 

 surfaces. 



Cleavage means a change in the space-relations of the 

 original egg-substance. With the formation of new cell- 

 partitions, especially in totally cleaving eggs which form 

 blastulae, the subdivision into cells means new disposition 

 of materials which at first were in more intimate contact. 

 The orderly arrangement of blastomeres may be looked 

 upon as one of the most characteristic attributes of the 

 cleavage-period. The cell-surfaces are not simple ones 

 but are made up of prolongations of unequal distribution, 

 length, and activity. 



With cleavage, then, by virtue of the ectoplasm, the 

 original egg-substance is separated into blastomeres and 

 the blastomeres are integrated by means of intercellular 

 connections, that is, the ectoplasmic prolongations. It is 

 well known that cells in a strip of tissue, like a strand of 

 ciliated epithelium, behave differently when part of the strip 

 and when isolated. The beating of the cilia can be observed 

 in an intact strip to run in order from one cell to the next; 

 whereas when the cells are isolated the cilia beat irregu- 

 larly. The same phenomenon has been observed in sus- 

 pensions of spermatozoa.^ In a normal sperm-suspension 



1 Lillie, F. R., /g/J. 



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