THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 109 
These data may be summarized as follows:! 
Species of Pheeno- 
cystes compared. 
Species.* 
Non- 
vacuolate. Vacuolate. 
Confined to exeretory tract-..-.-2-2..-2-...-22---....-- 14 0 
Commion sto both tracts) o- ec econ essence =e eeee hs 1 2 
Limited to nonexcretory tracts..-........-.------------ 1 22 
Number of 
“occurrences.” 
sie 
bc ” im 
Occurrences. pe 
vacuolate fVacuolate,. 
species. 
opal Sse sae es seme anses = -acuse sa aceaesetamar sas 37 | 44 
inrexcretony tract’. 32 -2/cs 1s sececacceuassscte loess 33 4 
io MONeXCLvevOMypUna Chae eesen ease ce secant eens see 4 40 
* Omitting the dubious ‘‘kidney’’ species and occurrences, and the somewhat 
questionable occurrence of Myzxobolus ellipsoides in the gall bladder. i 
ORGANAL DISTRIBUTION OF THE VACUOLE. 
From an examination of the above table it will be seen that the range 
of the genus Myxobolus throughout the organs is a wide one, but that it 
is almost strictly complementary to that of the Chloromyxide, Cystodis- 
cide, and Myxidiide. 
The real significance of these peculiarities of organal distribution 
lies, however, not so much in the peculiarities of generic-organal distri- 
bution, interesting as these are, as in the fact that these limits of the 
distribution of the genera in the organs almost exactly coincide with the 
limits of the presence of the iodinophile vacuole in the subclass, nearly all 
of the nonvacuolate Phenocystes being confined to the excretory tract, 
while nearly all the vacuolate Phenocystes are absent from this tract. 
Two questions immediately suggest themselves: 
1. Is it possible that the function of the vacuole is here even remotely 
shadowed? The constancy of the vacuole in the spore and the incon- 
stancy of vacuoles (? genetically related ) in the myxosporidium would 
seem to indicate that it functions during the spore stage. One sup- 
position which suggests itself is that in some way it might subserve 
oxygenation, but it is more probable that it serves as a food reservoir 
for the sporoplasm (cf. Thélohan’s comparison of its micro-chemical 
reactions with those of glycogen; p. 208). Unfortunately the origin of 
the structure and the phenomena of its disappearance after the exit of 
the sporoplasm have not been worked out. 
‘Tf the dubious occurrence of Myxobolus ellipsoides in the gall bladder be excluded 
as not proven. In any case the exceptionally wide organal range of this species 
should be considered in estimating the value of its occurrence in unusual seats, 
