MYXOSPORIDIA 309 



Various axial nomenclatures which have been suggested and 

 used by different authors, have led in many cases to confusion in 

 descriptions. The w^riter has defined a group of terms necessary 

 for accurate understanding of the spore (Kudo, 1920), which has 

 been used also by Calkins (1926) and Wenyon (1926). 



There are from one to four polar capsules at one end of the 

 spore except in the family myxidiid^ and genus Wardia. This 

 end is called the anterior end, and the opposite, the posterior end. 

 The axis connecting these two ends is the length of the spore. In 

 the case of Leptothcca or Ceratoniyxa, sutiiral diameter is used in 

 its place, since the breadth exceeds the length. The larger diam- 

 eter of the spore measured at right angles to the length or sutural 

 diameter is the breadth; and the smaller one the thickness of the 

 spore. In the family myxidiid^, there is a polar capsule at each 

 pole ; the axis connecting the poles is taken as the length ; the 

 larger diameter at right angles to it is the breadth, while the 

 smaller one the thickness. In spores with posterior projections, the 

 length of the spore is the distance between the anterior end and 

 the inner margin of the posterior end of intrasporal cavity and the 

 distance between the latter to the end of the tail or prolongation 

 is the length of the tail. The sum of the two makes the total 

 length of the spore. 



The front view of a spore is the one in which its length and 

 breadth are visible ; the side Z'ic7<' is the view in which the length 

 and thickness lie horizontally ; the end incw is the one in which the 

 breadth and thickness are observable. 



MATERIAL 



Although MYXOSPORIDIA inhabit various parts of the host body, 

 they could conveniently be divided into those which inhabit the 

 organ-cavities of the host and those which attack the host's tis- 

 sues or cells. The latter forms (histozoic or cytozoic myxospori- 

 dia) frequently produce conspicuous pathological changes in the 

 host and have been discovered on numerous occasions by persons 

 engaged in other studies of the fish. 



When tissues near the body surface or of the fin, are invaded 

 by MYXOSPORIDIA, the infected lesions may show striking growths 

 of tumors. An examination of a very small portion of their con- 

 tents would usually reveal an enormous number of spores. The 

 gills are very frequently infected and, aside from a few cases of 



