i8 PROTOZOA AND DISEASE 



or several cysts may be formed one within another. So far, 

 Rhumbler's account must be accepted as the established mode 

 of encystment ; what follows is, as explained above, of great interest, 

 but subject to explanations other than that given by the author, 

 which is briefly as follows : 



Sporocyst Formation. A duration-cyst, as described above, having 

 been formed, and the animalcule reduced to a round homogeneous 

 ball of plasm, with a marked opalescent appearance, the outer layer 

 of the animal becomes converted into a second thick cyst-wall, the 

 intervening space being filled with a clear fluid. All distinction 

 between nucleus and plasm is lost, the former having probably become 

 diffused in the plasm. Sporocysts may form within division-cysts in 

 half an hour; complicated cysts thus arise (Fig. 3 ; p and 10}. 



Such sporocysts placed in nutrient fluid under the microscope 

 became of a clear grey colour, and presented ten to twelve bright 

 bodies like oil-drops (Fig. 3 ; 12); these doubled in size in two days. 

 At the end of this time some of the cysts burst, and the small bright 

 bodies escaped (Fig. 3 ; 14). Rhurnbler thought at first that they 

 might possibly be synchytrians (vegetable parasites), but he was 

 able to trace them through the various stages (Fig. 3 ; 15 to 20), 

 which include amoeboid and flagellate forms, up to the original 

 ciliate form. If we imagine encystment occurring in parasitic 

 protozoa among the crowded elements of an infected tissue, we 

 should expect the shape of the cysts to be modified by compression, 

 or the formation of a capsule altogether aborted. 



The sporocyst state of a colpoda within a duration-cyst, * a 

 round, homogeneous ball of plasm,' corresponds to many pathological 

 appearances some, no doubt, real degenerations of tissue-elements, 

 but others, besides the corpuscles of Molluscum contagiosum, may be 

 true parasitic protozoa. When molluscum bodies are macerated in 

 water, well-defined capsules that were previously invisible often 

 appear. 



