THE MYXOSPORIDIA, OR PSOROSPERMS OF FLSHES. 189 



first tlieir existence is appreciable by the microscope, soon (July) they 

 are visible to the naked eye, the lower end of the zooid tube losing 

 its transparency and becoming milk white. In August the alteration 

 becomes very marked, the cavity of the zooid being distended and 

 completely opaque. 



Sjyore formation. — How and whence do the spores originate? In any 

 case their origin is endogenous (in the endoplasm) and probably occurs 

 in the manner observed by Prof. Biitschli in Myxidiirni lieberl-Uhnii, 

 where a spore membrane is foi-med around a trinueleate globule. In 

 our case are often found, in the plasmodiam, nuclei in state of division. 

 Around such nuclei, which are still united by the threads of the spindle, 

 a resistant shell appears often to be present. Gould this be a spore? 

 Korotneff is able to confirm Biitschli's observation that spore formation 

 does not mark the end of the life cycle. In M. brijozoides, however, 

 the spores always appear at a definite period of that cycle, viz, after 

 the comjjlete disappearance of the nuclei of the host-cell. 



Spore. — Elongate-oval, resembling a melon seed, sharp anteriorly, 

 rounded off posteriorly. Shell extremely hard, very resistant, lustrous, 

 apparently with an opening at the sharp (anterior) end; no bivalve 

 structure demonstrable, though empty spores are not rare. Often, but 

 not always, two vacuoles are visible. In the spring he was able to 

 distinguish at the anterior end of the spore a glittering point whose 

 signification was unknown. It might possibly be a capsule (uemato- 

 cyst; Nessellcapsel). 



Habitat. — In very considerable numbers in the body cavity of Alcy- 

 onella fungosa (a fresh- water polyzoan) in the neighborhood of Moscow, 

 in the beginning of summer. The infection appears to be endemic, as 

 Korotneff has never observed it in southern Eussia and as it appears 

 to be absent from western Europe. 



Seat and pathological anatomy. — Principally grouped around the 

 funicle upon which the spermatoblasts (which serve as food for the 

 young myxosporidia) are produced. No tissue except the spermato- 

 blasts is attacked. Eepeated careful investigations showed the absence 

 of myxosporidia from the polyp and from the walls of the zooecium. 



Effects. — The extensive infection exerts a direct (but only a mechan- 

 ical) influence on the polyp, producing, as a result of its continued 

 growth, a progressive atrophy, which, by the end of August, results in 

 the complete disappearance of the polyp. The infection extends itself 

 through the colonies, scarcely a single zooid escaping. The death of 

 the colonics occurs much earlier than it would naturally under the 

 influence of cold. 



Remarks. — Henneguy and Thelohan believe the reference of this 

 form to the Myxosporidia absolutely justified, although the capsule has 

 not been demonstrated. 



