720 



ORDER: MYXOSPORIDIIDA 



development, on the part of the host, of a fibrous capsule, within which 

 occur the remains of host cells with their hypertrophied nuclei, and the 

 multinucleate plasmodia containing a varying number of spores. The 

 central portion of such an encapsuled area, owing to degeneration of the 

 central part of the parasite, may consist of granular debris and spores, 

 while thee apsule itself is lined by the multinucleate cytoplasm of the 

 parasite, which continues to grow and produce spores. In old nodules 

 spores and debris alone may be detected, while later still fibrosis or even 

 calcification may occur, and all trace of the parasites be lost. 



Infection is brought about in the first place by the small amoeboid 

 organism, which frequently has two nuclei, escaping from the spore in the 

 intestine of the host. It is claimed by some that at this stage syngamy 

 takes place, but the evidence of this is conflicting. The amoeboid 

 organism, which is now known as a planont, makes its way to that par- 



FiG. 305. — Miixoholus pfeifferi .- Section through the Body of a Barbel, showing 

 Two Tumours caused bt the Parasite. (After Keysselitz, 1908.) 



ticular tissue or body space which the species infects. In some cases it is 

 evident that a multiplication of these small forms occurs, and this may 

 take place within the cytoplasm of cells, in the intercellular spaces of the 

 tissues, or in the lumen of the gall bladder or other body cavities. Finally, 

 growth into the large multinucleate plasmodia takes place. It was main- 

 tained by Cohn (1896) that Myxidium lieherhuhni, which infects the 

 gall bladder of fish, was able, in the multinucleate phase, to bud from its 

 surface numerous small uninucleate forms. Laveran and Mesnil (1902a) 

 showed that no such budding takes place in this species, and that the 

 formation of numerous short pseudopodia, and the fact that young para- 

 sites often become applied to the surface of older ones, are responsible 

 for the misconception. They showed that multiplication takes place by 

 equal or unequal division of the young forms. Kudo (19226) has, however, 

 described a process of internal budding in the case of Leptotheca ohlmacheri 

 in the kidney of the frog (Fig. 311). 



