MORPHOLOGY AND TAXONOMY OF THE SPOROZOA 545 



parasites of vertebrates and are transmitted by leeches, ticks and 

 rnites (Fig. 218). 



Fig. 218. — Type of Hemogregarines. A, Haemogregarina stepanowi; B and C, 

 Lankesterella ranarum. (Original.) 



Class II. CNIDOSPORIDIA Doflein. 



The Cnidosporidia form an independent stem of the Protozoa 

 with no recognizable affinities with other groups. They are ame- 

 boid and, in the adult stage, usually multinucleated, thus resembling 

 the Mycetozoa. Encapsulated sporoblasts and general mode of 

 life as parasites show some resemblance to the Telosporidia but the 

 life cycle is less complicated, sexual dimorphism and change of hosts 

 being absent. Unlike the Telosporidia reproduction does not 

 bring the life of an individual to an end but takes place more or 

 less continuously throughout the trophic stages, the sporoblasts 

 being carried about with the more or less active organism which 

 ultimately may become a relatively huge mass of spores. 



Sporulation and sexual processes are entirely different from 

 analogous activities in the Telosporidia. In a typical form of 

 Myxosporidia in which the ameboid body is multinucleated and 

 the nuclei frequently dimorphic, sporulation begins with a peculiar 

 process of internal budding. An island of protoplasm is formed 

 about two of the nuclei, one of each kind if dimorphic, and this 

 island was termed a pansporoblast by Gurley. This gives rise to two 

 cells, each with 7 nuclei after the 2 nuclei have divided to form 14 

 nuclei which are now all alike. Two of these 7 nuclei disappear 

 with the formation of a bivalved capsule, 2 of them disappear 

 with the formation of peculiar nematocyst-like capsules termed 

 35 



