4 
No. 403] NOTES ON A SPECIES OF PELOMYXA. 547 
in water under an unsupported cover, may be seen with a 
Zeiss y to enter into the composition of the surface film. 
This now appears as a row of microsomes connected by 
strands. On the other hand, when the Pelomyxa is examined 
under a supported cover-glass with a dry lens, the superficial 
membrane has an appreciable thickness and is plainly doubly 
contoured. Blochmann! mentions that in his Pelomyxas the 
* Hautschicht " seems to have a double contour. The doubly 
contoured appearance of the surface membrane is, I believe, 
due to the arrangement of the superficial meshes (alveoli of 
Biitschli), which, as Biitschli? has shown in so many cases, are 
arranged in a layer with the partition walls vertical to the 
surface. That is, the membrane appears doubly contoured, 
because we see the outer and inner walls of the meshes of the 
superficial layer, and fail to distinguish the partition walls 
between the several meshes. Under slight pressure the retic- 
ular (alvéolar) structure comes into view. 
In these few notes on the finer structure of the cytoplasm I 
have used the terms “ microsomes ” and “ reticulum " as indicat- 
ing the optical appearances obtained, and not with the intention 
of expressing a belief that the structures as such have an actual 
existence. 
In P. palustris the regularly arranged coarse granules, de- 
scribed above as present in vacuolar walls, are not figured by 
Gould (oc. cit.). In P. carolinensis they may easily be seen 
in the living specimen. The regularity of their arrangement 
at first sight suggests that they are not, to use some apt 
expressions of Mrs. Andrews,® mere * passive chemical inclu- 
sions,” but are “ physiological areas or substance organs," t.e., 
permanently differentiated portions of the living substance. 
On the other hand, they are not always present throughout the 
extent of the vacuolar wall, and in many vacuoles are absent or 
nearly so. The presumption is thus a fair one that the bodies 
are mesostates, and owe their regular arrangement (in places) 
to the underlying fine reticulum. 
1 Kleinere Mittheilungen über Protozoen, Biol. Centralbl., Bd. xiv. 
2 Investigations on Microscopic Foams and on Protoplasm. 
8 The Living Substance, p. 16. Boston, 1897. 
