$0 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
In Thelohania the myxosporidium appears to be absent (completely 
transformed into pansporoblasts?); the pansporoblast constantly pro- 
duces 8 spores. 
The process in Cystodiscus is imperfectly known (see p. 280). 
Nothing is known of the process in Spheromyaxa. 
The rule in Myxobolus appears to be pansporoblastic spore formation 
with tripartite sporoblast segmentation. Although at first sight M. miil- 
leri appears to constitute an exception to the rule, I have endeavored 
elsewhere (p. 218) to show that this species really conforms to it. 
Chloromyxum (as represented by C. leydigit; also C. incisum) through- 
out all its various habitats is characterized by monosporogenetic pan- 
sporoblastic spore formation. In C. mucronatum, however, Lieberkiihn 
appears to have observed 2 spores in the pansporoblast. 
Nothing is known of the process in Spherospora. 
In Myxosoma also nothing is known beyond the fact that the spores 
are developed within a myxosporidium., 
‘Beyond the very striking peculiarity of bisporogenesis, nothing is. 
known as to the process in Ceratomyxa (see p. 274). 
Myxidium (M. lieberkiihnii) appears to be characterized by pansporo- 
blastic spore formation, without sporoblast segmentation. As, however, in 
M. lieberkiihnii the developed capsule isa structure plainly separate from, 
and not continuous in substance with, the sporoplasm, its. abstriction 
from the latter must occur at some period of the development. As this 
abstriction would differ from the Myxobolus segmentation mainly in the 
time of its occurrence, the real amount of difference between the 2 pro- 
cesses becomes problematical.' : 
HISTORY. 
From the following (which, unfortunately, I have been unable to 
examine further) it seems to me probable that Leuckart recognized the 
pansporoblast as early as 1847. In speaking of the spores, he says:? 
Their formation takes place in an endogenous manner in the interior of special 
cells, as I havealready shown in another place (Géttingische Gelehrte Anzeiger, 1847, 
p. 1032). 
Leydig’s description? is as follows: 
A clear pale-contoured vesicle is first differentiated, in which a number 
1 Prof. Biitschli (Bronn’s Thier-Reich, 1882, 1, p. 600) takes, apparently with special 
reference to this species, the view that the capsules seem to lie not near, but in the 
sporoplasm, which appears to cover them with a delicate prolongation. This view 
is also, he remarks, to be expected from the developmental history. This, however, 
doubtless means only that the capsules are surrounded on all sides by the sporoplasm, 
not that they are continuous in substance therewith. 
2 Archiv. f. physiol. Heilkde, 1852, x1, p. 485. 
3Muller’s Archiv., 1851, p. 226. Ley¢lig, it will be remembered, erroneously regarded 
this structure as a vesicle (Tochterblase). His observations were made upon Chloro- 
myxum leydigii and C. incisum, 
