16 H. E. JORDAN 
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3 
Fie 3 Illustration of a fixed and stained specimen of a contracting muscle 
fiber from the lobster’s antenna, showing a reversal of striation as regards a 
deeply staining substance of the Q-dise of the relaxed portion (above) of the 
fiber (according to Dahlgren and Kepner). J, light disc; Q, dark dise; Z, telo- 
phragma; MW, mesophragma; m, extensions of telophragmata into perinuclear 
sarcoplasm; conn.t., tendon fibrils which attach the muscle to the hypodermis. 
Fig. 4 Illustration of contraction wave on living leg-muscle fiber of Dytiscus 
marginalis (according to Schaefer). The ‘apparent’ reversal of striae in the 
formation of the contraction bands of the middle portion is explained by Schaefer 
as due to accumulations of sarcoplasm, appearing as dark lines, which obscure 
the continuity of the fibrils and by contrast cause the whole of the sarcomeres 
between them to appear light. The writer interprets this illustration as being 
in strict accord with the illustrations of fixed and stained fibers, figures 1,2, and 3; 
therefore, as demonstrating a true reversal of striae, in the formation of the 
contraction band, as regards a deeper colored substance of the dark dise. 
