THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. ot 
Finally that, in at least one species, dispersal could hardly take place 
by the myxosporidium is shown by Biitschli’s observation! that in 
Myxidium lieberkiihnii that structure dies rapidly when removed from 
its natural habitat (the urine of the pike) to even “indifferent fluids.” 
(3) The myxosporidium, on the other hand, is the post-embryonic, 
comparatively stationary, growth-reproduction stage: There is little 
reason to suppose that there is ever any migration from one host to 
another during this stage. The evidence all points to the conclusion 
that after (and probably soon after) its attachment to the host, the 
valves of the spore separate, freeing the sporoplasm, which thencefor- 
ward is known as the myxosporidium. Thus Lieberkiihn, Balbiani, 
Pfeiffer, and Perugia have all seen the sporoplasm leave the spore 
and exhibit amoeboid movements. 
Now, if this view as to their relative functions in the life-cycle be 
correct, the capsular filaments may conceivably serve in several ways. 
First, they may serve as a flagelliform swimming apparatus, a view 
that [ think quite improbable, dispersal being more probably effected 
by currents, ete. Second, they may (and this is probably their most 
important function) serve for attachment.’ 
Further, if it be conceded that, after attachment, motion is necessary 
to the spore, the filaments might easily subserve such function either 
by a maximum extrusion, fixation of the tip, and a subsequent coiling- 
retraction (similar to that of the Vorticella stem), the spore in this case 
progressing “ anterior ” end foremost, or by a minimum extrusion fol- 
iowed by fixation of the tip and progressive uncoiling-protrusion, the 
spore in this case being pushed “ posterior” end foremost. In Glugea 
anomala, which has but one filament, 504 long, motion could hardly be 
effected in the latter way. But such motion is easily conceivable with 
the 2-capsuled (Myxrobolus, ete.) spores; and if it were admissible to 
suppose that the final lodgment preliminary to reproduction is ever 
effected by the spore and not by the myxosporidium, the latter being 
liberated and growing in situ (a view which, however, the present 
evidence tends to negative), this backward motion would be the best 
possible for inserting the spore under a scale, especially for those species 
provided with a tail, which latter structure would form an efficient 
guide to such insertion. IL incline, however, to the view that the func- 
tion of the filament is attachment, and that the motion necessary for 
the attainment of a place for reproduction-encystment is effected by 
the liberated myxosporidium. 
1 Ztschr. f. wiss. Zool., 1881, xxxv, p. 639. 
2 Perfectly consonant with this view is the observation of Biitschli (Ztschr. tf. wiss. 
Zool., 1881, XxXv, p. 635) that the filaments are extruded in spores which are pre- 
served a long time in water. For we thus see the floating spores ready for instant 
attachment to any object with which they may come into contact. A possible cause 
for such extrusion might perhaps be found in osmotic pressrre (preponderant endos- 
mosis from the surrounding water) from within. At any rate, it is difficult for me to 
attribute the rupture of the shelled-out cyst observed by M. Thélohan (see p. 221) . 
to any other cause. 
