nn 
ul! i : : 
i ¢ « 
i ll 
ita in hlliws*° : 
a. 2a 
ae Mn 
Wits, 
; i 
TW 
C 
Fic. 2 (A, B, C, and D) Four successive functional stages of ‘a leg-muscle 
fiber of the sea-spider, Anoplodactylus lentus. Fiber A is in the relaxed con- 
dition, fibers B, C, and D in successively later phases of contraction. Identical 
stages, in the same seriation, are met with when the four fibers are considered 
in a horizontal direction (between the telophragmata, Z), and when fiber D is 
considered in a vertical direction. This correspondence between the order of 
succession of the different levels of fiber D and the order of seriation of the four 
fibers would seem to prove this horizontal seriation correct. During contraction, 
therefore, the deeply staining substance of the Q-dises of the relaxed fiber (A) 
divides and flows in opposite directions from the midline (mesophragma) toward 
the adjacent telophragmata (B), meanwhile involving the N-dises (C) and uniting 
about the telophragmata (D) to form the contraction bands (Cb) of the con- 
tracted fiber. There occurs here a true reversal of striation as regards the deeply 
staining substance of Q during the formation of the contraction bands. The 
H-dise is a coincidence of contraction. Fiber D is stretched in its middle portion 
(according to Jordan: Anat. Rec., vol. 10, p. 493, 1916). 
13 
