286 



THE SPOROZOA 



(3) Morphology of the Spore. In their external form and 

 structural details the spores of Myxosporidia show great variability, 

 and furnish useful characters for purposes of systematic classifica- 

 tion. The spore -membrane is composed of a transparent, homo- 

 geneous substance, of doubtful chemical nature, and remarkable for 

 its resistance to the action of reagents. It has the form of two 



FIG. 92. 



Spore - formation in Thdohania 

 millleri (L. Pffr.). a, sporont with 

 single nucleus ; b, c, division of the 

 nucleus ; d, first division of the 

 sporont ; e, the two nuclei commencing 

 to divide again ; /, further stage, the 

 cells beginning to divide again ; g, four- 

 cell stage ; h, sporont containing eight 

 cells sporoblasts embedded in an 

 intercellular residuum ; i, the sporo- 

 blasts becoming spores ; j, spore with 

 single nucleus ; k, nucleus of the spore 

 dividing ; I, spore with two nuclei ; ra, 



gj & H spore which has been three days in the 



^ gut of a new host, and which has four 



// / /// nuclei. After Stempell [111], x 2250. 



valves meeting in a suture, along which the spore opens to permit 

 the escape of the sporozoite. The spore, as a whole, is very minute 

 in the Cryptocystes (4/^x3^ in Glugea anomala, 2'5,/tx 1*5 /4 in 

 G. ovoidea), and in this sub-order is uniformly pear-shaped. In the 

 Phaenocystes, on the other hand, the spore is larger, and often of 

 considerable size (100//,xl2/u,in Ceratomyxa sphaerulosa), and it is 

 always distinctly bilaterally symmetrical about the sutural or vertical 

 plane. In Leptotheca and Ceratomyxa the spore is elongated in a 



FIG. 03. 



Spore of Ceratomyxa sphaerulosa, Thel. (par. Mustelus and Galeus), x 750, after Thelohan. 

 sp.p, sporoplasm ; p.c, polar capsules; s, suture; x, "irregular, pale masses, of undetermined 

 origin." 



direction at right angles to the plane of symmetry (Fig. 93) ; but 

 in Myxidium, Henneguya, and most other genera of Phaenocystes, the 

 longest axis of the spore lies in the plane of the suture (Figs. 95, 

 99, 107, etc.); a position intermediate between these extremes is 

 occupied by the nearly spherical spores of Sphaerospom (Fig. 106). 

 The spore-membrane may be prolonged into tails or processes of 

 various kinds (Figs. 108, 112, etc.), which may attain a consider- 

 able length, in which case they are found coiled round while still 



