ON THE CLASSIFICATION OF THE MYXOSPORIDIA. 
411 
spore is symmetrical on either (right or left) side of the' vertical plane,* but it is asym- 
metric on either (anterior and posterior) side of the transverse plane. On the other 
hand, if, as seems probable, the generic reference of G. ? diploxys sp.nov. be correct, then 
“ends” in Cystodiscus are ends, properly speaking. It is needless to emphasize the 
taxonomic import of these results, for we are thus enabled to orient the spore aud the 
results of such orientation may be summed up as follows: 
1. Within this order the most important characters are the position and grouping of 
thecapsules. Compared to this the mere number of these bodies is a character of minor 
importance; for not only has Myxobolus 1 or 2 aud Cystodiscus 2 or 4, but the number 
even varies in the same species, Myxidium Ueberkuhnii Biitschli having 2 or 4.t 
But whether 1 to 2 or 2 to 4, the topographic relations are never varied. Thus in 
Myxobolus they are always in one group at the anterior end; in Cystodiscus in two 
groups, anterior and posterior ; and in Myxidium in 2 groups, right and left. 
Similar results are obtained with relation to the position of the valves, or, in other 
words, to the orientation of their plane, of junction. 
The following table shows the relations of these points to generic lines : 
Comparison of generic characters in the Phcenocystes. 
[X=present; 0=absent; () =less usual; — = condition not known.] 
Symmetry. 
Capsules. 
Shell. 
Vac- 
uole. 
Tail. 
Antero- 
poste- 
rior. 
Bilat- 
eral; 
perfect. 
Number. 
In one 
group 
(at the 
anterior 
end.) 
In two groups. 
Bi- 
valve. 
Inclination of 
plane of junc- 
tion of valves 
to longitudinal 
plane. 
At the 
(anterior 
and pos- 
terior) 
ends. 
In the 
(right 
and left) 
wings. 
0°. 
90°. 
X 
x 
2 (or 4) 
X 
X 
X 
0 
0 
x 
2 (or 1) 
X 
X 
X 
X 
0 
0 
x 
2 
X 
X 
x 
x 
x 
0 
X 
4 
X 
X 
(?) 
0 
0 
0 
X 
2 
X 
2 
0 
0 
0 
X 
2 
X 
X 
0 
0 
0 
(I) 
2 
X 
x 
x 
o 
0 
0 
X 
2 (or 4) 
X 
0 
0 
0 
'Imperfect. Shell and capsules symmetrical; sporoplasm unilateral. 
2 From analogy and general similarity of appearance, this genus can hardly be other than bivalve. 
*Tke three planes to which symmetry may be referred may be thus defined : 
Vertical plane: Median, longitudinal and intercapsular in position. 
Transverse plane: Vertical^, transverse and (in Myxobolus) postcapsular in position. 
Longitudinal plane: Horizontal, longitudinal and percapsular in position. 
tBalbiani, 1883, Journ. de Microgr. Paris, vu, p. 274, fig. 64 g. 
