NEOSPORIDIA 



181 



Sub-class. NEOSPORIDIA, Schaudinn. 



Sporozoa in which growth and spore formation usually go on 

 together. 



Order. Myxosporidia, Biitschli. 



These parasites, which were discovered by Johannes Miiller (1841), live principally 

 in fishes, and occasionally cause destructive epizootics amongst their hosts. Muller 

 first observed them in the form of whitish-yellow pustules on the skin or on the gills 

 of various fishes. These pustules contained masses of small shell-covered bodies with 

 or without tails ("psorosperms," see fig. 93). Similar bodies were also found in the 

 air bladders of certain fish. Creplin (i 842) demonstrated the resemblance of the cysts 

 ("psorosperm tubes") harbouring the psorosperms to the "pseudonavicella-cysts " of 

 a gregarine, as described by v. Siebold. Dujardin (1845) considered that there was 

 possibly some connection between the protoplasmic "psorosperm tubes" and the 

 spores they contained, and the developmental stages of monocystid gregarines from the 

 vesiculae seminales of earth-worms. The relationship of the " fish psorosperms ;J was 



FIG. 93. Upper figure, part of 

 a gill of a roach, Leucisciis rutilus 

 (natural size), with two myxospo- 

 ridia. Lower figures, a, b, d, spores 

 of myxosporidia from a pike, Esox 

 ludus. c, Spore from Platystoma 

 fasciatum. (After J. Miiller.) 



FIG. 94. The tailless spore of 

 Myxobolus *rtf/7crs, with the polar 

 bodies and their nuclei and the 

 sporozoite. (After Butschli.) 



placed on a firmer basis by Leydig (1851) and Lieberkiihn. The former found numerous 

 forms in marine fish, and he discovered in species which live free in the gall bladder 

 of cartilaginous fishes that the psorosperms originated in a manner similar to the 

 gregarines. Lieberkiihn (1854) studied the Myxosporidia in the bladder of the pike 

 (fig. 93, a, b, </), and observed their amoeboid movements, as well as the formation of 

 the spores, from each of which a small amoeboid body escaped, a discovery that 

 was confirmed by Balbiani. The same author also found that spiral filaments were 

 enclosed in the so-called polar body, i.e., the polar capsule of the psorosperm spores, 

 and that these could be protruded (fig. 93, d, and fig. 95). 



The term Myxosporidia, which at the present day is universally applied to the 

 "psorosperm tubes," was introduced by Biitschli in 1881, who studied not only the 

 structure and development of the spores, but also the protoplasmic body of the 



