408 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
CLASSIFICATION OF THE SUBCLASS. 
The only classification ever proposed is that of Tlielohan.* This author enunciates 
three taxonomic principles : 
1. The habitat furnishes no sound basis for specific distinctions, t 
2. The myxosporidium affords no taxonomic criteria. 
3. The spores alone offer (at least in the present state of our knowledge) characters 
suitable to serve as a basis for classification. He says: 
By noting the differences of form and size of these elements, the number of their polar cap- 
sules, by taking account of the presence or absence of a vacuole in the plasma, of their number in the 
[pansporoblasts!:, one can, I believe, succeed in obtaining elements sufficient for an attempt of this 
kind. 
Tlielohan further states that he regards the classification ouly as a provisional 
one, and that it is the result of a desire to obviate the great confusion arising from the 
habit of designating forms by their habitats. 
The following is Thelohan’s primary classification : 
MYXOSPOKIDIANS. 
Pyriform; capsule 1, at pointed extremity; vacuole 1, aniodino- ? 
pliile, at large extremity. > 
I. Glugeidians. 
Spores 
( Capsules 2 
No vacuole; capsules •{ 
II. Myxidians. 
Form variable 
( Capsules 4 
III. Ghloromyxans. 
Vacuole 1, iodinophile. Capsules 1-2 
IV. Myxobolans. 
The three principles mentioned, which form the basis of Thelohan’s classification, 
are unquestionably sound as far as they go, but to obtain a satisfactory arrangement 
it will sometimes be necessary to employ additional characters and to arrange them 
in a different order of rank. Especially will it be necessary in the Phcenocystes to refer 
constantly to the symmetry and topography of the spore. 
Further, while there can be no question as to the propriety of drawing a sharp 
line between the “ Glugeidians ” of the above table and the remaining Myxosporidia , 
*Bull. Soc. philomat. Paris, 1892, iv, pp. 165-178. 
t While as a general principle this is beyoud question, indications are not wanting to show that 
in some cases the seat and, to a somewhat less extent, the host, bear some relations to generic lines. 
One of the most significant facts of organal and zoological distribution is the following: 
Forms. 
Total number 
of species. 
Gall and uri- 
nary bladders, 
bile ducts and 
urinary 
tubules. 
Remaining 
organs. 
9 
Very many . . . 
8 
Adplur 2 (3 ?) 
1 
All but 2 (or 3). 
t Pansporoblast : The transparent plasma-sphere formed by the condensation of a portion of the 
plasma around one of the numerous nuclei of the endoplasm of the myxosporidium; in distinction 
from the sporoblasts which result from the segmentation of the pansporoblast. 
