288 



THE SPOROZOA 



or they may be situated at the two opposite poles, then termed 

 inferior and superior, as in Myxidium (Fig. 107); perhaps a good 

 example of a distinction without a difference. In Chloromyxidae 

 four capsules are found, which again may be in one group at 

 the anterior pole (Fig. 108), or disposed in two pairs at opposite 

 extremities, after the fashion of Myxidium. 



In Glugeidae the spores are remarkable for the fact that the single 

 polar capsule is invisible in the fresh condition of the spore, hence the 

 name Gryptocystes. It can, however, be demonstrated either by provoking 

 the extrusion of the filament or by the action of certain reagents which 

 render it distinct. The presence of a polar capsule in the spores of the 

 Glugeidae was first made known by Thelohan, a discovery which threw 



p.c. 



Spores of Glugea 6om- 

 byeis, Balbiani (par. Bom- 

 byx mori, etc.) a, 6, 

 spores seen in the fresh 

 condition, x 1500. c, d, 

 spores treated with nitric 

 acid, which causes them 

 to swell up a7id increase 

 in size by a half, at the 

 same time rendering the 

 polar capsule distinct. 

 In d the filament is ex- 

 truded. 



FIG. 99. 



Spores of Myxobolus miilleri, Butschli 

 (on the left), and Henneguya psorosper. 

 mica, Thel. (on the right), treated with 

 iodine solution to show the manner in 

 which this reagent colours the iodino- 

 philous vacuole (iod.vac) characteristic 

 of the Myxobolidae. p.c, polar capsules ; 

 pr, tail-like process. (After Thelohan, 

 X 1500.) 



light on the relationship of these forms, and led to the amalgamation in 

 modern classifications of the Myxosporidia (Phaenocystes) and Microsporidia 

 (Cryptocystes), formerly regarded as equivalent orders. 



The polar capsules are a very remarkable and distinctive feature 

 of the spores of Myxosporidia, and have often been misunderstood. 

 Mingazzini, for example, mistook them for the true sporozoites. It is 

 nevertheless possible that the polar capsules may represent sporozoites 

 modified and specialised for a particular function (for which see below, 

 p. 290), as suggested by Delage. It is difficult either to criticise or to 

 support this view until more is known of the relationship between the 

 Myxosporidia and other types of Sporozoa. 



The sporozoite, or sporoplasm, consists of a finely granular mass 

 of protoplasm. There is never more than one such body, which 

 has constantly two nuclei in Phaenocystes. In Cryptocystes, as we 



