752 MICROSCOPIC FORMS OF ANIMAL LIFE PROTOZOA 



for regarding it. like the ' conjugation ' of protophytes, as a true 

 generative act. 



The Coccidia (fig. 584) are Sporozoa which look like minute ova, 

 and which are found resting within the cells of their hosts ; the young, 

 developed from spores, are falciform in shape, and, moving about 

 actively, are able to penetrate fresh cells. They have been found in 

 the epithelium of the intestine of various forms, and in the liver of 

 vertebrates. Some parasites found in the blood (Haemamcebidse), 

 such as Drepanidium ranarum. Lankester, are allied to the Coccidia, 

 but are distinguished by having naked spores. Their chief interest 

 lies perhaps in their relation to various forms of malaria. 1 Among 



FIG. 584. Coccidi.li iii ovifonne (Leuckart) from the liver of the rabbit : 

 a, cyst just formed; &, condensed contents, the outer envelope has 

 disappeared ; c, contents divided into four sporoblasts ; d, the sporo- 

 blasts have become rounded and clearer internally; e and /, formation 

 of the falciform germ; g and ft, spores more highly magnified ffh'om 

 the side, // from in front. 



the Myxosporidia is Gluyea, the cause of the silkworm disease. The 

 Sarcosporidia are only known from the striped muscular tissue of 

 some vertebrates. 



Of the imperfectly known Myxosporidia it may be said that 

 their spores are the bodies which are known as ' psorosperms ; ' 

 while the bodies observed by Raiiiey and others, and wrongly 

 regarded as the cause of the cattle plague, are sarcocystids which 

 live in the muscular fibre of mammals. 



1 More and more interest is being taken in this subject, and some of the result s of 

 recent researches are of great interest and importance. Malaria appears to be due to a 

 Hsemamoebid which develops m gnats of the genus Anopheles ; when they arrive in the 

 human subject they appear as minute amcebulse which live in or on the ivd Mood 

 corpuscles ; they give rise to sporocytes which multiply indefinitely, or to sexual 

 gametocytes which undertake their sexual functions as soon as they enter the 

 stomach of gnats. See Ross and Fielding Ould, Quart. Jonni. Micr. ,SV/. xliii. 

 (1900) p. 571, and a very interesting ' Note on the Morphological Significance of the 

 Various Phases of Hiemamoebidte,' by E. Ray Lankester, torn. cit. p. 581. The 

 student should also consult M. A. Labbe's ' Recherches Zoologiques, Cytologiques 

 et Biologiques sur les Coccidies,' in Arch. Zool. Exper. 1896, p. 517 et *>'</., and Dr. 

 Wasielewski's Sporozoenkunde, Jena, 1896. A detailed bibliography will be found in 

 Prof. G. Sclmeidem Hill's Die Protozoen als Krankheitaerreger, Leipzig, 1898. The 

 various Memoirs of.Grassi, Lave ran, and Leger may be profitably studied. 



