546 THE AMERICAN NATURALIST. (VoL. XXXIV. 
some cases the strands are undoubtedly the free edges of folds. 
Some of the strands consist of a single row of comparatively 
large granules (intermediate in size between the microsomes 
and the coarse endosarcal granules), easily counted, and which 
are connected by the finest lines (fibres), in which no structure 
can be made out with 4, Zeiss. Other intravacuolar strands 
are of considerable thickness, appearing as a mass of finest 
granules (microsomes) closely set, in which a coarse granule is 
found here and there. Still other strands appear as exceedingly 
delicate lines, made up of one row of microsomes. 
In surface views of vacuolar walls, studied in sections, the 
same appearance is not always had. In many cases the wall 
seems made up of microsomes, arranged so as to give in places 
the appearance of a reticulum, the mesh of which is in the neigh- 
borhood of a micron. Interspersed among the microsomes 
much larger granules are found here and there, connected by 
fine strands, which often consist of a row of microsomes, 
though in other cases the connecting strand appears as a 
homogeneous line. In other vacuoles (always of considerable 
size) the wall when seen in surface view exhibits coarse gran- 
ules, set regularly and almost as closely as in the intervacuolar 
endosarc, between which run fine strands. If microsomes are 
present in such a wall, their presence is obscured by the coarser 
reticulum. 
The ectosarc in even a thinly expanded pseudopodium looks 
nearly homogeneous (4; Zeiss) in the living animal. In acetic 
carmine preparations mounted in glycerine, and in alcohol or 
acetic methyl-green preparations mounted in water, the ecto- 
sarc may be seen to be occupied by a delicate reticulum, the 
mesh of which is close to 1 u. I was not able to decide with 
certainty (working, however, only with Zeiss js) whether the 
microsomes are always situated at the points of intersection of 
the reticular lines (lamellae of Bütschli), or whether each (appar- 
ently) linear side of a mesh included a short row of microsomes. 
Dispersed in this delicate reticulum, which seems identical with 
that seen in many vacuolar walls, are to be found here and 
there a few coarse granules. 
The fine ectosarcal reticulum, in a fixed specimen examined 
