Harry Lewis Wieman ON 
opment is seen at this period. The evidence met with in this stage 
furnishes the most decisive proof in favor of a definite relationship ex- 
isting between the cyto-reticulum of the embryonic cell and the fibril 
bundles of the adult. Longitudinal sections present a very marked 
appearance of cross striations (Fig. 11,a; Fig. 12,a). On examination 
it is found that these striations are produced by a growth, principally 
in length, of the deposits on the cyto-reticulum of previous stages (Fig. 
9,a; Fig. 3,a). These heavily-stained bands stand out as clearly as if 
stamped with a die. Sections at this period present all gradations of 
striations as may be seen from Figs. 11 and 12. The transverse strands 
of the cyto-reticulum are not very prominent. The tapering ends of 
the cells show an enormous increase in length. It is to be noted that 
the striations first appear in the elongated ends, at least they show a 
greater degree of development in this part of the cell. These markings 
Qa 
ee 
3 
cause the ends of the cell to stand out more prominently than the other 
regions, and it is now very difficult to distingush cell walls in longitudinal 
sections. However, by means of the heavy striations, one can see how 
these slender projecting ends have made their way between other cells, 
and thus trace the formation of the syneytium-like structure of the 
adult tissue. In later stages, when the cell exhibits uniform striation, 
the course of the ends of the cells cannot be so well followed. The 
accompanying diagram would then represent the structure of the adult 
fiber in Jongitudinal section. This would also explain the fact that 
a cross section of the adult tissue, as for example, from a to b, shows 
cells of widely varying diameter. A similar explanation was offered by 
MacCallum, 98, in the case of the striated muscle of the pig. 
Fig. 12 shows the ends of two adjacent cells seen in the same section 
as Fig. 11, but which have apparently proceeded further in their develop- 
ment. The striations are well marked. In the figure several fibril 
bundles are represented (a). The structure found here corroborates the 
statement that the formation of the Querscheibe starts in the ends of 
the cells. 
