Figure 12. Transverse section of developing striated muscle fibres from an embryo 

 of Zoarces vivipara,A^ m.m. long. Note that the bundles of fibrils are still further 

 encroaching upon the achromatic myosyncytium. The fibrils on the periphery 

 of each bundle are still much thicker than those nearer the centre. The fibrils 

 of each group have not only become more numerous, but are also individually 

 thicker than those shown in Figure 11, which are of the same degree of magni- 

 fication. A nucleus surrounded by a clear undifferentiated zone of protoplasm 

 is shown in the midst of a large bundle of fibrils (above and to the right in the 

 Figure). X 1000. 



