84 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
anteriorly into a duct which pierces the shell near its anterior extrem- 
ity, affording exit for the filament. Wall usually taking (sometimes 
retaining, sometimes yielding up upon washing out) stains, especially 
the nuclear. Thélohan’ considers the substance composing the capsu- 
lar wall identical with that forming the shell, as both stain in the same 
way with safranin. From this view I must dissent, as in my experience 
not only the optical character, but also all the prominent staining re- 
actions, differ. In particular the capsules are wniformly opaque, the 
filaments never being visible through them, even in glycerin, while 
the shell is transparent in the highest possible degree. Further, in 
Myzxobolus macrurus (other species were not tried) bismarck brown and 
fuchsin each stain the capsule without even tinting the shell. 
Two reagents render the capsular wall transparent, thus permitting 
the filament to be seen coiled in situ. The first is iodine water (solu- 
tion with potassium iodide). This reagent also causes extrusion of the 
filaments, sometimes even in alcoholic specimens (pp. 85, 120). The 
second is strong ammonia water. I have never seen it produce extru- 
sion of the filament. 
Biitschhi? and Balbiani® have observed that when the filament 
is extruded there is (‘as in the thread cells proper”, Biitschli) a very 
marked diminution in the volume of the capsule, from which Biitschli 
infers that such extrusion is produced by the pressure of the stretched 
elastic capsular wall. 
This may be the cause of filament-extrusion, but might it not equally 
well be interpreted as the result of such extrusion or, more properly, 
as a co-result with the latter of a general increase of intrasporal pres- 
sure? However this may be, it seems very probable that the filament- 
extrusion which takes place under the influence of such energetic dehy- 
drants as sulphuric acid, glycerin, etc., is merely a physical effect, 
the result of the intense intrasporal endosmotic pressure. Thus in 
several species (among others, Myxobolus transovalis) sulphurie acid 
produces a pronounced swelling of the spore, extrusion (even in alco- 
holie specimens) of the filaments, and finally the expulsion of the cap- 
sules bodily, under an evidently great pressure. It can not, however, 
be denied that the action of iodine water is not thus explicable. 
Filament.—Exceedingly tenuous, attached at its proximal extremity 
to the capsular wall, free at its distal extremity; usually coiled into a 
spiral; in this condition entirely inclosed within the capsule cavity. 
Capable of uncoiling and of extrusion (via the capsular duct) as a semi- 
uncoiled or a fully uncoiled (nearly or quite straight) thread whose 
length may be many times that of the spore. That the semiuncoiled 
condition is merely an intermediate stage between the fully coiled and 
the fully uncoiled condition, and is not a specific character, is shown 
1Annal, de Microgr., 1890, m1, p. 207. 
2Ztschr. f. wiss. Zool., 1881, xxxv, p. 636. 
3 Journ. de Microgr., 1883, v1, p. 204. 
