PROTOZOA WITHOUT MOTILE ORGANS 67 



(The characteristics distinguishing these two suborders are not very definite, 

 and some more natural system should be worked out with further knowledge 

 of the group. Under the polysporous forms, for example, the genus Sphero- 

 spora is exceptional in having at least one disporous species and in having 

 nearly spherical spores.) 



Family 2. il yxidiidce, Thelohan, 1S92. The trophozoites are typically free-living 

 parasites in the fluids of the interna] organs of their hosts; the spore has two 

 polar capsules. 



Genus 3. Spherospora, Thelohan, 1S92. With spherical spores. Four or five 

 species, mostly from fish kidneys. 



Genus 4. Myxidium. Butschli, 1882. Spores navicular, with polar capsules at 

 each end. Seven or more species from kidney and gall-bladder of fishes and 

 tortoises. 



Genus .5. Spheromyxa, Thelohan, 1892. Spores navicular with truncated ends 

 and a polar capsule at each extremity. Polar filaments are short and thick, 

 and somewhat conical in form. Three species from the gall-bladder of 

 fishes. 



Genus 6. Cystodiscus, Lutz, 1889. Trophozoites without ameboid movement or 

 changes of form; spores symmetrical with the sutural plane running obliquely 

 from one extremity to the other and with a polar capsule at the extremities of 

 the obIic(ue suture. One species, C. immersus, Lutz, from the gall-bladder of 

 toads and Cystignathus in Brazil. 



Genus 7. Myxosoma, Thelohan, 1892. Spores flattened and ovoid in form and 

 with the polar capsules crowded together at the narrow extremity. One 

 species, M; dujardini, Thel., from the gills of Scardinius sp. 



Genus 8. Myxoproteiis, Doflein, 1898 (Myxosoma ambiguum of Thelohan and 

 Labbe). Spores somewhat pyramidal with spinous processes from the base of 

 the pyramid. One species, M. ambiguus, from the bladder of Lophius 

 piseatorius. 



Family 3. Ckloromyxidos, Thelohan, 1892. Spores with four polar capsules. 



Genus 9. Chloromyxum, Mingazzini, 1890. With the characters of the family. 

 Several species (six or seven) known and distinguished by presence of appen- 

 dages and distribution of polar capsules. 



Family 4. Myxobolidw, Thelohan, 1895. Typical histozoic parasites rarely found 

 in the ameboid form but usually as cysts filled with spores. Usually poly- 

 sporous, the spores with one or two polar capsules. The sporoplasm contains 

 vacuoles which are stained a reddish brown by iodine. 



Genus 10. Myxobolus, Biitschli, 1882. Spores ovoid or flattened into an ellipse. 

 Polar capsules single or double. A great many species (about forty) known, 

 and found in some organ or other of various fishes, and usually in the connec- 

 tive tissue of such organs. The genus is usually split up into three divisions, 

 the first of which contains the aberrant forms Jl. piriformis and M. unicap- 

 sulatus from the tench, with a single polar capsule and with jiear-shaped spores. 

 In the second are species ^\'ith spores having polar capsules of dissimilar size. 

 In the third are the great majority of the species referred to this genus, all 

 with polar capsules of similar form and size (Fig. 20, K). 



Genus 11. Hcnneguya, Thelohan, 1892. Ovoid spores with two polar capsules, 

 the sporocyst prolonged into two long caudal processes which are not pene- 

 trated by the sporoplasm. Four species from stickleback, pike, and perch. 



Genus 12. HofereUa, Berg, 1898. Spores broad and compressed with two tail- 

 like processes at the posterior end. One species, H. cyprini, Dofl., from the 

 carp. 



Order 2. Microsporidia, Balbiani, 1883. The trophozoites are more or less ame- 

 boid; the spores are very minute, piriform, and with only one polar capsule 

 which is invisible in the fresh state. They are typically parasites of inverte- 



