208 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
which the composition of the tail by the coaptation of a superior and 
an inferior half is easily demonstrable. 
In at least one species, however, this structure of the tail appears 
not to obtain. In Myxobolus macrurus the structure in question seems 
not to be a shell process at all, but an independent structure with dif- 
ferent optical and chemical properties. Although at first inclined to 
suspect the existence of the two lateral pieces (without the median 
piece; see p. 250) in the untailed forms, I was unable to detect any 
trace of them, as iodine failed to separate such a structure. Further, 
I was unable to prove the constancy of the initial posterior divergence 
of the valves which in M. macrurus I suspected to be correlated with 
the described structure of the tail. 
Sporoplasm.—Correlated with the typical number and position of the 
capsules is the characteristic peltate shape assumed by the sporoplasm. 
The shape and the topographic features of this structure are described 
in detail under Myxobolus macrurus (p. 251). The sporoplasm contains 
nuclei, an iodinophile vacuole, and “ granules.” 
Nuclei (see also “ granules” below).—These were first observed by 
Thélohan. He describes! the condition as follows: A series of spores 
properly stained shows some with 1 nucleus (frequently situated at or 
near the median cornua) and others with 2, 3, or 4 nuclei, everything 
pointing to their origin by division from the single one. The subse- 
quent ones appear to migrate at first outward and then backward. 
Vacuole (iodinophile)—Although visible on some of Miiller’s figures, 
Biitschli? was the first to direct attention to this structure. He 
described it as a nucleus, remarking that, though sometimes visible in 
the fresh state, it became more distinct upon the addition of acetic acid 
or iodine solution. He failed in his efforts to stain it, a result that he 
attributed to failure of penetration through the shell of the staining 
fluid. ® 
In 1889 Thélohan? corrected this erroneous interpretation, showing 
that the structure in question is a vacuole. Little differentiated in the 
fresh state (on account of similar refrangibility) from the sporoplasm, 
it becomes evident when the latter is coagulated by alcohol, acetic, 
nitric, or osmic acids, or by silver nitrate solution (2 per cent). Its 
chief micro-chemical characteristic is its extreme resistance to nuclear 
stains, which affect all the surrounding parts.’ Iodine alone stains it 
a brownish red, the remainder of the protoplasm taking a pale yellow 
hue. The iodine reaction exactly resembles that exhibited by glyco- 
1 Annal. de Microgr., 1890, 11, p. 210. 
2 Ztschr. f. wiss. Zool., 1881, xxxv, p. 636. 
2Compt. Rend. Acad. Sci. Paris, c1x, pp. 919-920. For Perugia’s confirmation see 
M, merlucii, p. 248. 
4Biitschli, indeed, states the contrary, but my own results are throughout in accord 
with those of Thélohan, as are also those of Perugia (Boll. Scientif., Pavia, 1891, x1, 
p. 24). 
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