3o8 RESEARCH IN PROTOZOOLOGY 



or at or near each extremity of the spore as in the family myxi- 

 DiiD^. In a few species of some eurysporid genera such as Wardia, 

 the polar capsules are not near any end, but even in such a case, 

 the foramina of the polar filaments are located at the anterior 

 end. 



The polar capsules may be pyriform or spherical in form. They 

 are situated at or near the anterior end of the spore. In myxidiid^ 

 one polar capsule is situated at each end, in which case no distinc- 

 tion is to be made between the anterior and posterior ends. The 

 number of the polar capsule in a spore, varies according to differ- 

 ent genera. There is only a single polar capsule in the spore of 

 unicapsular Myxobolus, Coccomyxa and Unicapsula, four in 

 Chloromyxum and Agarclla and two in all other genera. They may 

 be equal or unequal in size and form within one and the same 

 spore, although, as a rule, the former is the case. When two polar 

 capsules are located at the anterior end, they may be convergent 

 or divergent. Each has a foramen through the spore membrane in 

 or near the sutural plane ; occasionally the foramina may be so 

 closely located that they form one foramen as in the case of a 

 number of Myxoholus. Although the foramen is visible in fresh 

 spores, it often becomes more distinct when the spores are stained. 

 Each polar capsule contains a coiled polar filament which in most 

 species can be recognized without difficulty in the fresh condition. 

 The polar filament is, as a rule, a more or less long, most probably 

 hollow thread connected with the polar capsule. The filament is 

 extruded from the polar capsule through the foramen under the 

 influence of the stimulants such as the digestive fluid of the host 

 fish or certain chemicals (see p. 314). The filament is coiled along 

 the inner surface of the polar capsule, except in SphcBroinyxa in 

 which the distal portion of the filament makes the central axis with 

 the remaining part coiled around it. 



Each spore possesses, when mature, a single sporoplasm, except 

 in a few species in which there are two sporoplasms even in the 

 mature spore (see p. 312). The sporoplasm occupies the extra- 

 capsular cavity of the spore and is of usually granular structure 

 with two nuclei which are occasionally faintly visible in fresh 

 spores. In the family myxobolid^, there is an iodinophilous 

 vacuole mostly round or oval, which occurs in mature spores and 

 which is one of the important characters of the family. Small 

 refringent fat globules have also been seen in the spore. 



