MORPHOLOGY AND CLASSIFICATION 



parasites of this type are comparatively small and not very well 

 known. They are often spoken of as microsporidia or psorosperm^, 

 The best-known form is Nosema bombycis, the cause of Pebrine in 

 silkworms. 



Ciliates. The second substem of the protozoa, Ciliophora, 

 is distinguished by the locomotive organs, numerous cilia which 



FIG. 8 1. Diagram of the developmental cycle of Nosema bombycis. C, Cell of 

 the intestinal epithelium containing asexual multiplication forms and showing their 

 transition into spores, a, b, c, Spores, the last with polar thread, d, Ameboid form 

 emerging from the spore to penetrate a new host cell at h. (From Dofiein after 

 Stempell.} 



cover most of the body surface, and by the possession of two dis- 

 tinctly different nuclei, one apparently concerned with nutrition 

 of the eel] and the other definitely associated in an important man- 

 ner with the sexual reproduction. Multiplication takes place by 

 transverse division into two daughter cells or by budding. In the 

 parasitic forms this may take place within a protecting wall (cyst). 



