182 



THE ANIMAL PARASITES OF MAN 



parasites (fig. 96), and confirmed the occurrence of numerous nuclei. Many authors 

 have made important additions to our knowledge of the Myxosporidia : Perugia, 

 Thelohan, Mingazzini, L. Pfeiffer, L. Cohn, Doflein, Mercier, Schroder and Auerbach J 

 while the presence of this parasite outside the class of fishes has become known 

 through Lutz, Laveran, and others. The species causing disease in fishes have been 

 described by Ludwig, Railliet, Weltner, L. Pfeiffer, Zschokke, Hofer, Doflein, Gurley, 

 Plehn, Schuberg, Fantham and Porter. With regard to classification the works of 

 Thelohan (1895) an ^ Gurley (1894) may be mentioned. 



The Myxosporidia live either free on the epithelial surface of hollow organs 

 (gall or urinary bladder, renal tubules, but never in the intestine), or are enclosed in 

 the tissues of their host. The gills and muscular system are their favourite 

 habitat, but other tissues or organs may be attacked. Species of Myxosporidia 

 are also known from Amphibia, Reptilia, and a few invertebrates. 



The free forms, which are often amoeboid (fig. 96), move by the aid of variously 

 shaped pseudopodia, have a constant form, or may exhibit contractions of the body. 

 The tissue parasites often reach a considerable size, so that the integument of the 



FIG. 95. Schematic representation of a 

 spore of Myxobolus. One polar capsule has 

 protruded its filament ; two nuclei and a 

 " vacuole " in the sporozoite. (After Doflein.) 



FlG. 96. Chloromyxnm leydigi. Active 

 trophczoite (parasitic in gall-bladder of skates, 

 rays, dog-fish). Ect, ectoplasm ; ps> pseudo- 

 podia ; end. endoplasm ; y, yellow globules 

 in endoplasm ; sfi, spores, each with four 

 polar capsules, x 525. (After Thelohan.) 



host forms protuberances over them. They are of a roundish or irregular shape 

 Frequently they are enveloped in a connective tissue covering formed by the host. 



The protoplasmic body in the trophic phase (fig. 96) shows a distinct ectoplasm 

 which is finely granular or sometimes striated, and an endoplasm which is coarsely 

 granular and contains many nuclei as well as cell inclusions, such as crystals, pig- 

 ment grains and fat globules. The nuclei originate by division from the primitive 

 nucleus of the amoeboid germ that issues from the spore. This amcebula may or 

 may not live intra-cellularly during the early stages of its existence. 



The multinucleate trophozoite of a Myxosporidian forms spores in its endoplasm 

 practically throughout its whole period of growth (fig. 96). Vegetative reproduction 

 by a process of external budding or plasmotomy may also occur, as in Myxidium 

 lieberkiihni from the urinary bladder of the pike. 



The myxosporidian trophozoite may produce two spores within itself, when 

 it is placed in the sub-order Disporea, or it may produce numerous spores, which 

 is characteristic of the sub-order, Polysporea. The phenomenon of spore formation 



