9 8 



COMPARATIVE ANATOMY 



time the sarcolemma is formed as a delicate membrane 



bounding the fibre. Presently cross as well as longitudinal 



striae make their appearance and invade the whole periphery 



of the fibr.e, the nuclei imbedded in a core of granular 



Fig. 18. 



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

 showing the nuclei , and the protoplasm p, of the 

 coenocyte 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 ; />', 

 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.) 



protoplasm occupying the centre. Eventually the striation 

 and fibrillation extends to the centre, and the nuclei move 

 outward to take up a superficial position under the 

 sarcolemma. Thus it appears that, although the striated 



