154 Victor E. Emmel. 
8. a. Regenerating striated muscle is ectodermal in origin. 
b. The myofibrille appear genetically related to the eyto-reticulum. 
Each fibril is early surrounded by a sheath of modified cytoplasm, 
multiplies by longitudinal splitting, and in its differentiation the “z” 
line or membrane of Krause, becomes evident after the formation 
of the light and dark bands. 
e. The muscle fiber or cell is multinuclear when first formed. Later 
the nuclei come to be peripheral in position while the fibrille he 
to the side of the fiber nearest the center of the muscle bundle. The 
nuclei multiply by mitotic division, and with the development of the 
sarcolemma they become flattened and elongated in the long axis of 
the fibers. 
d. The myofibrille differentiate throughout their whole length into 
true striated muscle elements, except in the region of skeletal attach- 
ment. There the peripheral ends of the fibrils remain unstriated, 
and serve as tensile elements. 
e. The connective tissue over the inner surface of the epidermis, 
and the purely supporting fibrille within the epidermal cells develop 
later, but these structures appear to be secondary in their relation to 
muscle attachment. 
9. a. The present observations indicate that the neurilemma is 
derived from the regenerating epidermal cells. 
b. During certain stages in the differentiation of the axis cylinder 
the finer neurofibrille are central and the coarser fibrils more per- 
ipheral in position. 
10. In at least certain regions of the regenerating limb, supporting 
and apparently true connective tissue differentiates from epidermal 
cells. ; 
11. a. In the development of the chitinogenous muscle plates and 
the myofibrille and their striz, differentiation appears to be neither 
directly “centrifugal” nor “centripetal” in direction. 
b. On the contrary, the facts warrant the statement that whatever 
sequence there may be in differentiation, it is correlated with the size 
and functional relations of the muscles concerned, rather than with 
any distal or proximal relation of these structures to the organism. 
