202 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
) 
the nuclei have time to return to astate of rest, whence they again pass 
through the same stages preliminary to division. 
The sporoblasts have no regular arrangement within the pansporo- 
blast membrane; their shape is inconstant, varying with their arrange- 
ment; they generally approximate a truncate-pyramidal form. Each 
sporoblast develops into a spore. Spores thus contained 8 in each 
pansporoblast membrane, without regular arrangement, not nearly 
filling the cavity. Thisis the last stage of development reached in the 
muscles of the host. 
Pansporoblast membrane retaining its original dimensions, perfectly 
transparent, very thin, although the double contour is easily visible, 
showing in optical section marked thickenings, often 2 in number (pl. 12, 
fig. 1k). 
(2) Development of sporoblast into spore: Owing to the very minute 
size of these bodies, it is almost impossible to follow this development 
in detail or to confirm the facts discovered in the larger forms by Thélohan, 
viz, sporoblast segmentation, number of nuclei, ete. 
Development of capsule: A peculiar arrangement, believed to be 
connected with the development of the capsule, was noted, viz: often in 
the body of the sporoblast, near the nucleus, a clear rounded space, into 
which a small protoplasmic button projects. This observation is, how- 
ever, a very delicate one, and the figures are slightly diagrammatic. 
Morphology of the sporophorous vesicles—The constitution and develop- 
ment of the spore-producing vesicles permit us to consider them only as 
the morphological equivalent of the pansporoblasts of the other A/yzo- 
sporidia. These octosporophorous pansporoblasts form a transition 
from the oligosporogenetic pansporoblasts of the larger species to the 
polysporogenetic pansporoblasts of Glugea, which latter produce a con- 
siderable and inconstant number of spores. Above all, one fact is here 
to be noted, viz, the entire absence of a myxosporidium. No structure 
whatever could be detected which could be regarded as its morpho- 
logical or physiological equivalent. 
But whence come these spore-producing vesicles? Evidently they do 
not represent the first stage of development. Now if, as is usual, they 
are formed in the interior of a protoplasmic mass, what has become of 
the latter? In all other known species a considerable protoplasmic 
residue remains, even of myxosporidia whose development is completed, 
and in which young pansporoblasts are no longer to be found, but only 
entirely mature spores. But here are young pansporoblasts at their 
simplest (uninucleate spherules) with not the slighest trace of a sur- 
rounding protoplasm. As long as we had only found these organisms 
in the mature state (as sporophorous vesicles) that absence might have 
been explained, in case of necessity, on the supposition of a complete 
previous transformation of the myxosporidium into pansporoblasts, the 
myxosporidium vanishing in the process or leaving only insignificant 
vestiges. But in the presence of the now known earlier phases of 
development this hypothesis seems hardly admissible. 
