SPOROZOON PARASITES OF FISHES. 207 



angles to the planes of the two polar capsules), and the mature spore of M. musculi 

 measures 14.3/i in length by G.jfi thick, and from 4 to 6.7^ in width (see p. 204), in indi- 

 viduals of apparently the same stage of development, it still seems that a sufficient 

 discrepancy in size exists to supplement the marked differences in the pathological con- 

 ditions. It may yet prove that the latter are due to the influence of different hosts, inas- 

 much as we have one case of a Fundulus with a typical M. musculi lesion, but having 

 spores indistinguishable from those of M. lintoni in either size or appearance. 



M. lintoni presents another contrast to the conditions in Fundulus. In the former, 

 calcareous bodies were observed amongst the spores by Linton (1889) and the writer, 

 whereas nothing of the kind has ever been encountered in the hundreds of Fundtdus 

 tissues which we have examined. 



Although the name M. lintoni was for a time retained for the Fundulus parasite, the 

 present state of our knowledge will not permit of this assumption. The species " musculi" 

 has been adopted because of the interesting and characteristic attack which the tropho- 

 plasm makes upon muscle fibers. 



The spore of Myxobolus oviforniis (Thelohan) resembles M. musculi very much in 

 appearance, but is less tapered and shorter (Thelohan, 1894). 



The following, for one reason or another, are also of interest in their bearing upon 

 M. musculi. A " Myxosporidian " of unknown genus and species was found by Linton 

 (1899) in the connective tissue of the entire body of Notropis megalops Rafinesque 

 (albeolus Jordan), the shiner. The epidermis is marked by dark purplish blotches. The 

 scales are absent in most cases. A "Myxosporidian" of unknown genus and species was 

 observed by Lieberkiihn (1854) in the connective tissue of Gasiereosteus aculeatus (stickle- 

 back). The skin is said to have contained cysts. The conditions seem to be unlike those 

 in Fundulus. Cyprinus leuciscus (Miiller, 1841) has been observed with tumors in the 

 integument caused by a species of Myxobolus. M. oblongatus Gurley produces cysts 

 under the scaleless skin of the head region in Catostomus tuberculatus Le Sueur (Gurley, 

 1891, 1893, p. 234). M. transovalis Gurley (1893) of Phoxinus (Clinostomus) fundidoidcs 

 Girard, occurs under the scales and external to the epidermis. " It forms a thin dis- 

 coidal mass situated in the center of the concave undersurface of the scale." That it 

 is not identical with M. musculi is certain from the dimensions of the myxospore (length 

 6/1, breadth 8/(), the diameter of which, at right angles to the polar axis, is greater than 

 through the polar axis. We have very scanty information concerning the M. strongylurus 

 (Gurley, 1893, p. 247), which is found encysted in the skin of the head of Synodontis 

 schal; of M. momurus (Gurley, 1891 , p. 416), known from cysts in the subcutaneous inter- 

 muscular tissue of Aphredoderus sayanus Gilliams; of Henneguya niisslini Schuberg und 

 Schroder (Leger, 1906), which is found in the connective tissue of the dorsal fin of the 

 trout; of M. gigas Auerbach (1907), which thickens the integument at the ventral angle 

 of the gill in Abramis brama Linnaeus (bream) ; and of a Myxobolus of unknown species 

 described by Borne in 1886 (Gurley, 1893, p. 244), which causes great tumors over the 

 surface of Leuciscus rutilis. 



In Coregonus jcra there occurs a common disease of the integument caused by a 

 species (M. zschokkei, Gurley, 1893; Zschokkei, 1884), the myxoplasm of which is not 

 known. The cysts lie in the subcutaneous connective tissue and between the muscles. 

 It causes irregular thick patches on the skin, from which the scales drop. 



