734 OEDEE: MICEOSPOEIDIIDA 



one vegetative nucleus and two generative nuclei. By a process of 

 gemmation or budding trinucleate individuals may be separated. In 

 tbis process the vegetative nucleus divides into two. One of these divides 

 again to form a vegetative nucleus and a generative nucleus. The latter 

 again divides to form two generative nuclei. Eound the group of these 

 three nuclei cytoplasm concentrates and the trinucleate bud is separated. 

 Apparently this process can be repeated several times, so that the number 

 of trinucleate parasites in the kidney tubules is greatly increased in number. 

 Spore formation takes place in the trinucleate forms, each generative 

 nucleus giving rise to one spore. The generative nucleus divides to form 

 two nuclei, and these again to form four. Of these four, two are devoted 

 to the formation of the two valves of the spore, one divides to form two 

 nuclei which give rise to the two polar capsules, while the fourth divides 

 to form the nuclei of the two infective amoeboid bodies which occur in the 

 fully-formed spore. Each generative nucleus of the original trinucleate 

 individual thus gives rise to six nuclei, so that a parasite in which two 

 spores are developing simultaneously, which is not always the case, will 

 have one vegetative nucleus and twelve generative nuclei, each group 

 of six generative nuclei being destined to form one spore. 



B. Order: MICROSPORIDIIDA Labbe. 1899. 



The parasites included in this order produce small spores, which are 

 frequently less than 5 microns in length. The spores often resemble 

 yeasts or bacilli, but possess one or, exceptionally, two polar capsules 

 from which, after treatment with certain reagents or under pressure, 

 exceedingly long filaments are extruded (Fig. 30). The latter may reach 

 a length of 500 microns or more. The organisms occur as intracellular 

 amoeboid parasites (Fig. 312). As multiplication takes place, the para- 

 sitized cells often become hypertrophied in a remarkable manner. In the 

 case of some hosts, only special organs are attacked, but in others, as in the 

 silkworm disease, the whole body is overrun by the parasites. The ova 

 may become infected, with the result that the parasites pass from the 

 parent to the ofTspring. After multiplication in the amcfiboid phase has 

 gone on for some time, certain spherical uninucleate forms (pansporo- 

 blasts or sporonts) undergo a complicated development to produce the 

 characteristic spores. The spores produced by each pansporoblast vary 

 in number from one to sixteen or more according to the particular genus 

 or species. 



The Microsporidiida are found commonly in the intestinal epithelium 

 and other tissues of the aquatic larvse of insects. They occur also in 

 certain vertebrates such as fish, in which tumour-like nodules may be 



