BINARY DIVISION. 85 



that remain, redevelop within the course of a few hours to the size and 

 form of the normal zooid. In Vorticella, Paramecium, and other hard- 

 skinned Infusoria a closely similar phenomenon of decomposition is mani- 

 fested under like conditions through the extension at various points of the 

 cuticle of globules of sarcode, this process, if not artificially or otherwise 

 arrested, continuing until the entire endoplasm has become dissipated. 

 Among the more minute monadiform animalcules a parallel form of disin- 

 tegration is preceded by the assumption of an entirely irregular and mostly 

 amrebiform contour, closely corresponding with such as accompanies the 

 processes of fusion or encystment ; the type Monas diffluens, figured and 

 described later on, affords a suitable example of this last-named phase. 

 Collectively, the very appropriate name of " diffluence " has been applied 

 by Dujardin to these several closely identical modes of decomposition here 

 enumerated. Similar phenomena, however, as they occur among' the 

 Ciliata were long before observed by O. F. Muller, who described them 

 under the several titles of " molecular effusion " and " dissolution." In 

 certain exceptional instances, including notably Halteria grandinella and 

 its allies, an apparent modification of the process of diffluence is exhibited 

 by the animalcule bursting suddenly to fragments in its mid career, without 

 any accompanying visible causes of irritation. 



REPRODUCTIVE PHENOMENA. 

 Binary Division or Fission. 



This mode of reproduction represents not only the earliest recognized 

 and most widely distributed, but undoubtedly that also by which under 

 normal conditions the specific infusorial form is most abundantly propa- 

 gated. As in all of the manifold structural aspects previously discussed, the 

 infusorial! body reproduces, with diverse modifications, the structural and 

 functional features only of a simple cell, so likewise this special mode of 

 multiplication is found to be a mere reflex of the ordinary reproductive 

 phenomena exhibited by the cellular elements or units of all higher tissue 

 structures. In these, from the most simple to the most complex, the 

 increase in size or growth of the tissue is effected through the indefinite 

 increase by binary or duplicative division of the specific type of cells of 

 which it is composed. The astonishingly rapid growth of certain cellular 

 tissues or structures, through such constantly repeated binary division of 

 the constituent cells, is too familiar for recapitulation, and almost equally 

 extraordinary figures are attained in connection with the multiplication 

 of the independent unicellular bodies of the Infusoria through this simple 

 process. Thus, Ehrenberg long since computed that in the case of Stylonychia 

 mytilus, no less than one million of independent beings were derived through 

 the simple and repeated fission of a single zooid in the course of ten days, 

 while in that of Paramecium aurelia, he reckoned that as many as 268 



