Figure 5. Developing striated muscle from a 23rci clay frog-embryo. The myosyn- 

 cytium shows the early stages of fibrillation. In the lower part of the figure is 

 a shrunken nucleus from the upper pole of which a large oval globule of achro- 

 matic material is seen extending upwards. Two other nuclei exhibit the 

 enlarged turgid condition which exists previous to the discharge of the nuclear 

 achromatic substance. X1500. 



