136 THE AMPH10XUS. 



seen. So far as this goes, the transverse section 

 make things thoroughly clear. In. these we are able 

 also to gain further information regarding the form 

 and growth of the muscle fibrilla. 



The muscle fibrilla come under our notice in the 

 transverse sections first as quite small bright granules 

 on the surface of the cells in contact with the noto- 

 chord (Figs. 124-127). The fibrilla grow in the fur- 

 ther course of the development to such an extent 

 that from being thread-like in form they become 

 strap-shaped. These strap-shaped fibrilla are parallel 

 to one another and in a somewhat acute angle on 

 the lateral surface of the notochord. They occupy 

 the interior half of the cells, at whose expense they 

 grow. Between the muscle bands remains at the 

 most only a very small remnant of protoplasm. This 

 is stored up in the outer club-shaped portion of the 

 cells (Figs. 130-136). 



These histological differentiations proceed from the 

 anterior to the posterior end. 



The prolongations of the anterior end of the first 

 mesoblastic somite differentiate also in the main 

 in the same way, with this difference, that the num- 

 ber of the muscle fibrilla is there smaller, answering 



