98 



COMPARATIVE ANATOMY 



striae make their appearance and invade the whole periphery 

 of the fibre, the nuclei ' imbedded in a core of granular 

 protoplasm occupying the centre. Eventually the striation 

 and fibrillation extends to the centre, and the nuclei move 



Fig. 1 8. 



A, embryonic striped muscle fibre from the tail of a tadpole, 

 showing the nuclei nJi, and the protoplasm /, of the 

 ccenocyte from which the fibres are developed. The fibres 

 exhibit alternate dark and light bands, and in the centre of 

 each dark band is a light line, the line of Hensen ; B, 

 cardiac muscle-fibre showing the short branched nucleated 

 cells ; C, a single cell from cardiac muscle - fibre, more 

 highly magnified, showing the cross striation and the 

 nucleus n. (A original; B and C from Schafer.) 



outwards to take up a superficial position under the 

 sarcolemma. Thus it appears that, although the striated 

 muscle-fibre is often spoken of as a cell-fusion it is in reality 

 not a product of many cells but of a ccenocyte. 



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