322 Sporozoa 



modern evidence indicates that, as in Nosema (75), Duboscqia (73), Bacil- 

 lidium, and Mrazekia (63), the single nucleus or the two nuclei of the 

 sporoblasts become the corresponding nuclei of uninucleate and binu- 

 cleate spores. Accordingly, it appears that somatic differentiation and 

 division of labor, as seen in the Myxosporida for example, are lacking in 

 the Microsporida. 



Taxonomy 



Classification of the Microsporida is based primarily upon the form 

 and structure of the spores and to a lesser degree upon differences in the 

 details of sporogenesis. Four families have been recognized (71). 



Family 1. Coccosporidae. The spores are spherical, or approximately 

 so, and contain one polar filament. The family contains the genus Cocco- 

 spora Kudo (71; Fig. 6. 31, A, B). 



Family 2. Mrazekiidae. The spores have a single polar filament and are 

 cylindrical, or tubular and curved. The ratio of length to thickness is 

 greater than 5:1. 



The family includes the following genera: Bacillidium Janda (64; Fig. 6. 31, P, Q), 

 Cougourdella Hesse (71; Fig. 6. 31, R), Mrazekia Leger and Hesse (64; Fig. 6. 31, C), 

 Octosporea Flu (64; Fig. 6. 31, D, E), Spiroglugea Leger and Hesse (71; Fig. 6. 31, F), 

 and Toxoglugea Leger and Hesse (71; Fig. 6. 31, G). 



Family 3. Nosematidae. The spores are usually ovoid or pyriform; if 

 more elongated, the ratio of length to thickness is less than 4:1. There 

 is only one polar filament. 



The following genera have been assigned to the family. Duboscqia Perez (73; Fig. 6. 

 31. I), Glugea Thelohan (137; Fig. 6. 31, L), Gurleya Doflein (71; Fig. 6. 31, U), 

 Nosema Nageli (75, 76; Fig. 6. 31, H, T), Plistophora Gurley (Fig. 6. 31, J, K), Pyrotheca 

 Hesse (71), Stempellia Leger and Hesse (71; Fig. 6. 31, S), Thelohania Henneguy (Fig. 

 6. 31, M) and Trichoduboscqia Leger (71). 



Family 4. Telomyxidae. The single genus, Telomyxa Leger and Hesse 

 (71; Fig. 6. 31, N, O), is characterized by spores with two polar filaments. 



Order 4. Helicosporida. This order was erected by Kudo for the genus 

 Helicosporidium Keilin (68). The single known species, H. parasiticum, 

 was found in larvae of a ceratopogonid dipteran, Dasyhelea obsciira, from 

 sap in wounds of elm and horse-chestnut trees. All stages of development 

 occur in the body cavity of the host. Occasionally, however, parasites were 

 found in fat bodies and in nerve ganglia, the invasions resulting in 

 destruction of the fat bodies and reduction of the ganglia to neurilemma. 



Young trophozoites grow and divide, frequently producing groups of 

 eight (Fig. 6. 33, A-D). Sporulation is preceded by a period of rapid 

 multiplication, and each spore apparently is developed from a group of 



