THE LIVING SUBSTANCE, 



95 



shortening axis of the body would thicken as they shortened ; 

 while those having a transverse direction would of course thin 

 as they elongated with the mass. The alveoli too, would then 

 become more widely separated as the fibrils shortened, and 

 would draw nearer together as these elongated. But it is just 

 the converse of this that I found to take place in Epistylis, — 

 for there the alveoli approach each other along the shorten- 

 ing, and become more widely separated along the lengthening, 

 fibrils. 



If we attempt to explain the phenomena simply by change 

 of shape of the alveoli under tension stress, as in Biitschli's 

 tentative hypothesis of contraction, the conditions exacted are 

 just those needed in Greeff's explanation, and hence cannot be 

 in place here. Especially are these things true, if the pres- 

 ence of the finer foam be taken into consideration, as indeed 

 it must, for, during relaxed moments, the interalveolar sub- 

 stance showed filose phenomena, extending itself into the 

 inclusions of Biitschli ; the alveoli regained locally more 

 rounded contours during general contracted states ; and the 

 strial substance even split into strands, or became visibly, 

 though very minutely vacuolate ; and during local contractions 

 in these strands the alveoli slipped slightly along the striae, 

 or had their optical network drawn into triangles, or other 

 figures. 



Closer observation showed that the increased emphasis in 

 the striae was due to an actual displacement of interalveolar 

 substance during contraction. During displacement of the 

 mass in any direction, the interalveolar material forming the 

 last emphasized set of striae was in great part displaced, 

 the displacement being an actual one, and following, as it 

 seemed, lines of least resistance between the yielding alveoli 

 filled with fluid ; which may be prepared paths. The contrac- 

 tion wave which urged forward the substance, drew together 

 the alveoli, and as the activity had the usual wave-like prog- 

 ress, the cross striae became progressively increased in mass by 

 access of interalveolar stuff. The ectosarcal mode of organi- 

 zation of the elements as typically seen in this cuticle of 

 Epistylis, and which is characteristic of all areas of organized 



