THE ECTOPLASM 



its activity is limited to the surface. On more general 

 grounds, it may be pointed out that it is held that muscle- 

 contraction, ciliary action and amoeboid movement are 

 similar and have a common basis. Ectoplasmic threads 

 may be considered as fine amoeboid processes, delicate 

 pseudopodia; a cilium may be regarded as a modified 

 pseudopodium. On the basis of my suggestion the striae 

 of a cross-striated muscle can be regarded as threads of 

 ectoplasmic substance, and muscle as a strand compounded 

 of pseudopodial processes. 



This suggestion of mine concerning the origin of the 

 muscle-fibre from repeated building of sheets of ectoplasm 

 is interesting in the light of a passage from Lewis and Lewis 

 in their "Behavior of Cells in Tissues"': 



There are three conditions resembling fibrillac, which are 

 often observed, not only in heart-muscle cells, but in smooth 

 muscle, endothelium, and mcsothelium as well; namely, a 

 linear arrangement of long mitochondria, an overlapping of 

 long, slender processes, and tension striations. The latter 

 deserve most consideration, because they resemble closely 

 the appearance of iibrillae in fixed cells. Migrating cells 

 become more or less flattened out on the solid supports 

 under considerable tension. The direction of this tension 

 appears to be in line with the cell processes, as though the 

 latter produced a pull on the ectoplasmic layer. The visible 

 striae of various widths and lengths thus produced in the 

 living cell are not permanent but may disappear and new 

 ones may appear in line with new processes. The exact 

 significance of these striations is uncertain. They may 

 extend across the nucleus, indenting it or almost cutting it 

 in two. They seem to be a phenomenon produced by ten- 

 sion and reversible when the tension is altered or relaxed. 

 On fixation they may retain their identity and stain more 

 deeply than the rest of cytoplasm, resembling myo-fibrillae. 

 The latter occur however in fixed cells which do not show 

 tension striae. 



Certain nerve-cells are also notable for their fibre-like 

 nature. Among these are the longest cells known. One 



^ Lewis and Lewis, Lc. 



8i 



t 



