THE MYXOSPORIDIA, OR PS0R08PERMS OF FISHES. 189 



first their existeuce is appreciable by the microscoiDe, soon (July) tbey 

 are visible to the naked eye, tbe 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 

 comiiletely opaque. 



Spore formation. — How and whence do the spores originate'? In arxj 

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

 in the manner observed by Prof. Biitschli in Myxldinm lieberl-iihuiij 

 where a spore membrane is formed around a trinucleate globule. In 

 our case are often found, in the Plasmodium, 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 x>resent. Could 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. hryozoidcs, however, 

 the spores always appear at a definite i^eriod of that cycle, viz, after 

 the complete 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 sj^ring 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 (nemato- 

 cyst; Nfissellmpsel). 



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

 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. 



Scat and pathological anatomy. — Princij)ally 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 zooBcium. 



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 colonies occurs much earlier than it would naturally under the 

 influence of cold. 



Remarks. — Henneguy and Thelohan believe the reference of this 

 form to the ALyxosporidia absolutely justified; although the capsule has 

 not been demonstrated. 



