RHIZOPODS, ACTINOPODS, SLIME MOLDS, SPOROZOA 99 



protozoan parasite, its lack of host specificity is so extreme that 

 many workers recognize only a single species occurring in a wide 

 variety of birds and mammals and in various tissues within the 

 host. Electron microscopy (Gustafson, Agar, and Cromer, 1954; 

 Meyer and Andrade Mendonca, 1955; Ludvik, 1956) reveals a 

 set of characteristic anterior organelles : a polar ring and conoid 

 like those of Sarcocystis, and extending posteriad from within the 

 conoid a group of 14 to 18 longitudinally oriented, claviform 

 threads, 80 to 120 m^ in diameter, called toxonemes. In addition, 

 longitudinal pellicular fibers diverge from the polar ring. The 

 cytoplasm more posteriorly is of conventional appearance and 

 contains bodies believed to be mitochondria, in addition to a 

 nucleus with a distinct membranous envelope. Lainson, Baker, 

 Bird, Garnham, and Healey (1961) report that Lankesterella (placed 

 with the coccidiomorphs in the Grasse treatise) resembles 

 Toxoplasma. 



The similarity in structure of the anterior organelles in Sarco- 

 cystis and Toxoplasma is too great to be ignored, and it seems likely 

 that taxonomic rearrangements are in order. It is unquestionably 

 premature to draw similar conclusions with respect to these two 

 organisms and Plasmodium; but the apical ring, peripheral fibers, 

 and paired organelles variously reported by the Garnham group, 

 the Duncan group, and Meyer and Oliveira Musacchio invite 

 further comparative study. 



Anaplasma is yet another infectious organism, whose classifica- 

 tion as a protozoan has seemed highly dubious. Recent electron- 

 microscope studies (Foote, Geer, and Stich, 1958 ; Espana, Espana, 

 and Gonzales, 1959) leave the question still open. Foote and 

 colleagues sectioned infected bovine erythrocytes and found 

 wagon-wheel-shaped structures that seemed to be particulate in 

 nature; they concluded that the organism is probably a virus. 

 Espana and co-workers, however, found in particulate prepara- 

 tions of hemolyzed erythrocytes an opaque, spherical head, up to 

 1 /x in diameter, and a long, curved tail; these often were associated 

 in pairs as rings, dumbbells, or open triangles. According to these 

 authors, motility can be detected by phase-contrast study of living 

 organisms. 



Members of the Subphylum Cnidosporidia develop their 

 ameboid sporoplasms within a spore that also contains one or 



