542 THE AMERICAN NATURALIST. [Vor. XXXIV. 
be taken as characteristic of the adult condition, since the 
Pelomyxas were always picked out with the unaided eye, no 
effort being made to discover young forms with the micro- 
scope. i 
Structure of the Body. — There is a perfectly clear peripheral 
(ectosarcal) region, which in the living state is very narrow, 
being conspicuous only at the ends of expanding pseudopodia 
(Fig. 8. The granular, more opaque and fluid endosarc con- 
tains numerous nuclei, vacuoles, and other bodies. Though 
the endosarc is naturally lighter near the edge than further 
in, this difference in transparency is due to a difference in 
thickness and not to a difference in composition. The nuclei 
are very abundant, and scattered without order through the 
endosarc. They are elliptical in shape, and measure 18 p X 16 4 
(typical case). The vacuoles in the endosarc vary greatly in 
size. Large ones, distinct with an az (Zeiss) objective, and 
often measuring 40 4 in diameter, are scattered about in some 
abundance. When the body is compressed, or when sections 
are examined, the,endosarc is seen to be honeycombed with 
vacuoles of all sizes; the very small ones, a few microns in 
diameter, being especialy abundant. So abundant are the 
vacuoles in parts of the endosarc that the optical effect (in 
section or thinly expanded pseudopodium) is that of a spongy 
reticulum. 
There is no contractile vacuole in this form. If a vacuole 
disappears, it does so simply because of the shifting of the pro- 
toplasm. The endosarc contains in the greatest abundance 
minute crystals, which contribute very materially to its dark 
appearance with transmitted light. These bodies are of an 
elongated fusiform shape, about 24 in length. When seen 
end on, they look like dots. They are readily soluble in alco- 
hol and in dilute acetic (used in acetic carmine and methyl- 
green solution), but are neither stained nor dissolved by one per 
cent osmic. Their diminution in size and gradual disappear- 
ance, when treated with the above solvents, may be watched 
under thé microscope. It requires but a few minutes for them 
to vanish completely, leaving the other inclusions much more 
distinct than they formerly were. 
