





Millimeters 



Figure 59. — Transverse section of tensilium showing lamellar structure and darkly pigmented surface, C. virginica- 



Photomicrograph of unstained and nondecalcified preparation. 



suggested that electron microscopy might reveal 

 some interesting details. Small pieces of the 

 resilium fixed in 1 percent osmic acid were em- 

 bedded in plastic and sectioned. Although the 

 material is ver\' hard, it was possible to obtain 

 sections from 0.3 to 0.5ai in thickness. The 

 electron micrograph (fig. 61) shows bands of 

 fibrils varying in diameter from 370 to 500 A. 



A section made across the plane of the arches 

 (fig. 62) shows a membrane honeycombed by holes 

 about 500 A in diameter. Two interpretations 

 seem possible: (1) that the fibrils are tubular, 

 the light areas corresponding to the centers of the 

 tubes, or (2) that the empty circles represent 

 spaces between the fibrils. The first interpreta- 

 tion is more plausible because of the gradation 



THE LIGAMENT 



53 



