ie all 
THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 201 
never showed, under the most careful microscopic examination, the 
slightest trace of infection (Henneguy and Thélohan, 1892). 
Season.—Disease most frequent and at maximum of development 
from about July 15 to the end of August; number affected diminishing 
in September; diminution more pronounced in October; disappearing 
entirely after November 15; reappearing about March 15 or the first 
days of April. 
32. Thelohania giardi Henneguy, 1892. PI. 12, figs. 1, 2. 
Crangon 
poe ate giardi. | Date. Authority; reference. 
etc., of. 
Se AR Seb Sepencsnas 1892 | Thélohan & Henneguy, Compt. Rend. hebdom. Soc. 
Biol. Paris, IV, pp. 586-7. 
Thelohania -| 1892 | Henneguy in Thélohan, Bull. Soc. philomat. Paris, 
IV, pp. 165, 174, footnote. 
Thelohania.| 1892 | Henneguy & Thélohan, Annal. de Microgr., IV, pp. 621, 
624, 626-31, pl. 4, figs. 9-25. 
x 1893 | Ohlmacher, Journ. Amer. Med. Assoc., XX, p. 562. 
Thelohania .| 1893 | Gurley, Bull. U.S. Fish Com. for 1891, XI, p. 410. 
Thelohania .| 1893 | Braun. Centralbl. f. Bakt. u. Parasitenkde, XLV, pp. 
739-740. 
Thelohania .| 1894 | Braun. Centralbl. f. Bakt. u. Parasitenkde, XV, p. 86. 
* Crangnon; error. 
Cyst unknown. 
Spore formation.—Pansporoblast spherical; diameter 14 jy (12 to 
14 yw); in the young stages consisting of a very thin membrane 
resisting potassiuin hydrate, inclosing a very transparent, scarcely 
granular, slightly refringent protoplasin, having at its center a rather 
large nucleus (pl. 12, fig. 1a, b), often visible in the fresh state, becoming 
much clearer under the action of reagents. 
(1) Segmentation of the pansporoblast: The nucleus first presents 
the typical resting structure with a distinct membrane. The chromatin 
can take on different arrangements, sometimes formingone grain much 
larger than the others, sometimes a variable number of smaller sub- 
equal grains, or sometimes crowded back against the membrane, pre- 
senting here and there thicker portions (pl. 12, fig. 1). Subsequently 
a remarkable modification occurs: the chromatin has beconre arranged 
in filaments, the membrane has disappeared, and the nucleus assumes 
the arrangement known as the chromatic coil; very soon the chro- 
matic filaments orient themselves into a very distinct equatorial plate, 
which becomes double, the process resulting in the formation of 2 
daughter-nuclei. We thus have atrue karyodieresis. The achromatic 
filaments were not seen, doubtless owing to their rather small size and 
partly, Henneguy and Thélohan believe. to the nature and optical proper- 
ties of the protoplasm. Protoplasmic segmentation soon follows nuclear 
division, and one sees, within the primitive pansporoblast membrane, 2 
small distinct nucleated masses. In their turn these 2 masses divide 
and redivide, the process ending with the formation of 8 small plasmic 
bodies (sporoblasts) within the original pansporoblast membrane. The 
divisions do not take place very rapidly, and between successive ones 
