THE NEOSPORIDIA 415 



be very similar in its general appearance to that of yeast-organisms, and 

 may result in the formation of chains of cells. When the host- cell is used up, 

 the meronts do not multiply further, but produce a final generation of uni- 

 nucleate cells which, as sporonts (Fig. 172, 13), give rise in this genus each 

 to a single spore. 



In the development of a spore, the nucleus of the sporont (sporoblast) 

 buds off three small nuclei (Fig. 172, 14), two of which, as parietal nuclei, 

 form the sporocyst, while the third is concerned with the formation of the 

 single polar capsule, and the fourth or principal nucleus remains as the nucleus 

 of the amcebula (Fig. 172, 15). Doubtless there are divisions of the proto- 

 plasm corresponding to the divisions of the nuclei, but in such minute bodies 

 they cannot be made out clearly. The sporocyst, when formed, is a tough 

 capsule, which, though produced by two cells, does not show any indications 

 of a double composition, but appears to be cast in one piece. In some species 

 only a single parietal cell has been seen. The spore as a whole (Fig. 172, 16, 

 1, 2, 3) is egg-shaped, with one end, commonly termed " anterior," narrower 

 than the other. It contains two vacuoles, one near the anterior, the other 

 near the posterior end. The single polar capsule is of relatively large size ; 

 situated axially in the spore, it occupies its whole length, and contains a polar 

 filament of immense length, wound spirally in its interior. In Glugea anomala 

 atoore 6 A* in length may eject a polar filament 150 n long (Stempell, 784) ; 

 whue in Pleistophora longifilis the filament may measure as much as 510 /*, 

 more than forty-one times the length of the spore (Schuberg). The existence 

 of a polar capsule is denied by Schuberg, who maintains that the filament 

 is coiled up within the posterior vacuole of the spore. 



The amcebula occupies the middle region of the spore, between the two 

 vacuoles, and apparently separating them ; but in reality it has the form of a 

 ring or girdle, wrapping round the axial polar capsule and filament, and 

 placed slightly nearer the anterior pole of the spore. The amcebula contains 

 at first a single nucleus, which, according to Stempell, divides into two and 

 then into four. Schuberg, however, maintains that the amcebula, and indeed 

 the entire spore, contains but a single nucleus ; he denies the existence of 

 parietal and capsulogenous nuclei, and in his opinion the bodies that have 

 been interpreted as such are in reality metachromatinic grains. Stempell's 

 description of the development of the spore is, however, in accordance with 

 that given by other investigators. 



When the spore germinates in the intestine of a new host, the polar filament 

 is shot out, and the amcebula creeps out through a pore at the anterior end ; 

 there would appear to be at this point a small cap which closes the spore, and 

 which is blown off by the explosion of the polar capsule (Fig. 172, 4). Accord- 

 ing to Stempell, the amoebula emerges from the spore with two nuclei, leaving 

 the other two behind in the sporocyst as reduction-nuclei ; then the two nuclei 

 of the amcebula copulate, in an autogamous manner, to form a synkaryon, 

 and the uninucleate amcebula that results initiates the generation of planonts. 

 It seems, however, not improbable that some process of copulation with other 

 amcebulse, liberated from other spores, may occur at this stage, and remains 

 to be described. 



A life-cycle similar in the main to that described for Nosema bombycis, 

 with planonts, meronts, and sporonts, as successive phases, is probably 



FIG. 172 continued: 



9 13, multiplication of the meront (schizont) in the cell, in two different 

 ways, the one shown in the series 9a, lOa, lla, 12a, 13a, the other in the series 

 9&, 10&, 11&, 12&, 12c, I2d, 13& : 13, a and &, young sporonts ; 14, divisions 

 of the nucleus of the sporont ; two small nuclei which have been budded 

 off at the lower end are the future parietal nuclei ; from the principal nucleus 

 the nucleus of the polar capsule is being budded off ; 15, 16, formation of 

 the spore, with two parietal nuclei, one capsulogenous nucleus applied to 

 the polar capsule, and the nucleus of the sporozoite, at first single (15), later 

 double (16). After Stempell (785), slightly modified. 



