THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. aoe 
acuate posterior extremity, destitute of apparent structure,’ very 
liable to break off, the fracture always taking place evenly and never 
producing a ragged end. Lateral pieces 2, strongly curved, extend- 
ing forward on either side from the anterior end of the median piece, 
applied closely to the rounded posterior portion of the shell about as 
far forward as the junction of the posterior and middle thirds of its 
outer margin; thickest at their origin, becoming very thin toward their 
anterior extremities. They have a slight expansion over the superior 
and inferior surfaces of the shell, thus tending to form a slightly cup- 
shaped receptacle for it. It is probable that they really extend forward 
along upon the surface and over the sides of the ridges, which struct- 
ures appear as though continuous with them. 
Capsules: 2, pyriform, somewhat diverging posteriorly, attenuated 
at the anterior end into the ducts which converge forward toward the 
median line, on either side of which they open. Capsular wall staining 
readily with and retaining tenaciously bismarck brown and fuchsin; 
rendered transparent by iodine water and by strong ammonia water. 
The filaments are thus seen lying coiled within the capsule. They 
appear not to stain with reagents which stain the walls, the capsule 
usually showing a lighter central and a darker circumferential portion. 
Relative to the occasional presence on or near the capsule of a dark 
‘“oranule,” see p. 220. The capsules are always surrounded by a 
clear space, the pericystic. This space never shows a double contour, 
never stains, and presents no appearance suggestive of an outer mem- 
brane. It is apparently a natural and presumably (by exclusion and 
analogy) a fiuid-filled space. It does not stain with iodine, agreeing 
in this respect with the space (with which it is continuous) everywhere 
lining the inner surface of the shell, and differing in the same respect 
from the vacuolic space. 
Sporoplasm: Inferior surface convex in all directions, showing a 
rounded postero-lateral margin,” extending from about the middle point 
of the lateral border of the spore on one side to the corresponding point 
on the opposite side. From these two points (infero-lateral cornua) 
the 2 antero-lateral borders curve inward and forward with a sharp 
anteriorly directed concavity to the median line where the sporoplasin 
is drawn out to a point (the infero-median cornu) which forms also the 
inferior extremity of a ridge shortly to be described as the supero- 
inferior intercornual ridge. The infero-median cornu is situated about 
at the level of the middle point of the antero-posterior diameter of the 
shell cavity. Lateral surface, extending forward for some distance 
1 Jodine (aqueous solution with potassium iodide) produces a decided beading of 
the median piece, transverse lines of division appearing, constituting a decided 
pseudo-segmentation. My attention was directed to this phenomenon by Dr. Stiles. 
2 Common, of course, to it and to the superior surface, being the line of intersec- 
tion of the longitudinal plane with the interior surface of the shell. 
