446 BIOLOGY OF THE PROTOZOA 



life cycle is less complicated and sexual dimorphism and change of 

 hosts are 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 is entirely different from that in the Telosporidia 

 and does not result from the metagamic divisions of a zygote. In 

 a typical form of Myxosporidia in which the amoeboid 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, termed a pansporoblast by Gurley 

 (1893) is equivalent to a sporocyst and gives rise to two sporoblasts 

 each with 7 nuclei after the two nuclei have divided to form 14 nuclei 

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

 formation of the bivalved capsule of the sporoblast; 2 of them 

 disappear with the formation of peculiar nematocyst-like capsules 

 termed polar capsules containing coiled threads, 1 is cast out of 

 the cell and 2 remain as the sporoblast nuclei which sooner, or 

 later, unite to form one a process of fertilization known as autogamy 

 (Fig. 180). 



The complications are thus of quite a different character from 

 those of the Telosporidia but they are not shown by all of the 

 Neosporidia, polar capsules, for example, being absent in Sarco- 

 sporidia. 



The group is so highly diverse that generalizations are impossible 

 apart from the very general statement that, like Telosporidia, they 

 may be lumen-dwelling (coelozoic), tissue-dwelling (histozoic) par- 

 ticularly of the muscle tissues, or cell-dwelling (cytozoic) in habitat, 

 and that new hosts are invariably infected by the contaminative 

 method, usually by way of the digestive tract. 



Compared with the Telosporidia the life histories and cytology 

 of Neosporidia are little known. Morphologically, however, more 

 advance has been made and enough to warrant the division into two 

 sub-classes— Cnidosporidia and Sarcosporidia, with an outline 

 classification as follows. 



Class Neosporidia, Schaudinn (1900). 



Sub-class 1. Cnidosporidia, Doflein. 

 Order 1. Myxosporidia, Biitschli. 

 Sub-order 1. Eurysporea, Kudo. 



Family 1. Ceratomyxidae, Doflein. 

 Sub-order 2. Sphterosporea, Kudo. 



Family 1. Chloromyxidae, Thelohan. 

 Family 2. Spluerosporidie, Davis. 



