THE STRUCTURE OF CELLS 



tion arises in connection with the fact that nuclear- and cell- (or 

 cytoplasmie-) division are by no means invariably associated, and 

 that although the cytoplasm never gives rise to a number of cells 

 in excess of the number of nuclei present, its divisions in other- 

 respects may occur independently of that of the nuclei. This is 

 seen in the cleavage of some animal eggs (e.g. mollusca), in the 

 formation of endosperm in the seeds of angiosperms, in the develop- 







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Fio. 8. 



Lilium martagnn, prophase of the first mitosis in the pollen-mother-cell, showing the longi- 

 tudinal fission of the cromatin and linin. 



ment of the eggs of Fucus and of the spores of Mucor. In all these 

 instances, the division of the nucleus precedes that of the cyto- 

 plasm, which is only subsequently partitioned. 



The first indication of approaching karyokinesis in an ordinary 

 somatic cell of the body of one of the higher plants or animals is 

 usually visible in the nucleus. The chromatin granules become 

 aggregated in lines, corresponding to a growing definiteness in the 

 delimitation of the linin. Thus from the generally granular appear- 

 ance, the character of a much convoluted and tangled chromatic 



