THE MYXOSPORIDIA, OR PSvOROSPERMS OF FISHES. 



201 



never showed, under the most careful microscopic examination, tlie 

 slightest trace of infection (Henneguy and Thelohau, 1892). 



Season.— Bisea^e most frequent and at maximum of development 

 from aboui 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 Ilemieguy, 1892. PI. 12, figs. 1, 2. 



Crangoa 



vulgaris, 



"parasite" 



etc., of. 



giardi. 



Thelohania 

 Thelohania 



Thelohania 

 Thelohania 



Thelohania 



Date.. 



1892 



1892 



1892 



1893 

 189:^ 

 1893 



1894 



Authority; reference. 



Thfelohan & Henneguy, Compt. Eend. hebdora. Soc. 



Biol. Paris, IV, pp. 586-7. 

 Hennoguy in Tlielohan, Bull. Soc. philomat. Paris, 



IV, pp. 165, 174, footnote. 

 Henneguy & Tliclohan, Annal. deMicrogr., IV, pp. 621, 



624, 626-31, pi. 4, figs. 9-25. 

 Ohlmacher, Journ. Amer. :Med. Assoc, XX, p. 562. 

 Gurley, Bull. V. S. Fish Coiu. for 1S91, XI, p. 410. 

 Braun. Centralbl. f. Bakt. u. Parasitenlide, XIV, pp. 



739-740. 

 Braun. Centralbl. f. Bakt. u. Parasitenkde, XV, p. 86. 



* Crangnon ; error. 



Cyst unknown. 



Spore /or»mtioj«.— Pansporoblast spherical; diameter 14 /< (12 to 

 14 yw); in the young stages consisting of a very thin membrane 

 resisting potassium hydrate, inclosing a very transparent, scarcely 

 granular, shghtly refringent protoplasm, having at its center a rather 

 large nucleus (pi. 12, fig. la, 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 forming one 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 (pi. 12, fig. 1). Subsequently 

 a remarkable modification occurs: the chromatin has become 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 a true karyodieresis. The achromatic 

 filaments were not seen, doubtless owing to their rather small size and 

 partly, Henneguy and Th61ohan believe, to the nature and optical proper- 

 ties of the protoplasm . Protopl asmic segm en tation 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 



