92 



ANDREWS. 



difference in mass, or quality, of the continuous substance. It 

 is often due to its interalveolar filose activities, but may result 

 from more stable local increment where the interalveolar foam 

 has a secretory or irritable function. 



Contractile striation, and even true fibrillation, appear some- 

 times in very fluid areas of protoplasm. Then alveoli will be 

 drawn into line, for the moment at least, along the course of 

 the optical striation. Many swift and evanescent contractions 

 of the fluid substance in protean forms or areas can thus be 

 traced, and causes and means of motion of the protoplasm of 

 amoeba and kindred forms can best be seen and followed. 



The line established by a contraction wave may be very tor- 

 tuous among the vesicles, and thus bring into line, by, or for, 

 organized action, those which were at first quite far apart. The 

 converse is obvious, and the value of such a method in forming 

 compound areas having enormous extension powers in given 

 directions must be great. 



It has already been stated that, from time to time, in areas 

 and masses, the living substance varies its viscosity, and hence 

 its optical qualities, becoming denser and more refractive 

 when viewed with powers too low to resolve structure. In 

 examining such protoplasm wherever possible under powers 

 adequate to resolve all, or part, of the foam structure, the physi- 

 cal modification was found to be due to like qualities in the 

 continuous, and chiefly in the interalveolar, material of the 

 visible structure, irrespective of size, or character of arrange- 

 ment, of the alveolar inclusions of Biitschli's structure. And 

 the continuous substance held these characters for just so long 

 as the area, as a whole or locally, held the optical characters 

 noted. And wherever, under high powers, the interalveolar 

 substance showed such characters in any area, however small, 

 that area under lower powers had a marked distinctness and 

 refractive quality which were persistent, or intermittent, in 

 sympathy with the same character in the continuous element. 



Further, those parts of the continuous element which had 

 more marked refractive quality, were visible as distinct structures 

 under powers which showed nothing of the rest of the network, 

 however one might isolate minute portions for examination. 



