64 ORGANIZA TION OF THE INFUSORIA. 



approaches in many instances the one last mentioned, while in others it 

 exhibits widely distinct features. Like the preceding, it is connected with 

 the phenomena of reproduction, but the encysted animalcule multiplies 

 itself not merely by the process of binary fission, but by the subdivision of 

 the encapsuled mass into a greater or less number of spore-like bodies 

 which, after a more or less prolonged quiescent state, develop to the 

 parent form. This type of encystation may be most appropriately 

 denominated "sporular encystment," and the cyst or capsule secreted 

 in such instances, a " sporocyst." Details of this special mode of multi- 

 plication are given in the section devoted to the subject of reproduction, 

 and it is only requisite here to indicate one important point in which such 

 sporular encystment departs widely from both of the preceding kinds. 

 In each of these latter the cyst or capsule produced is the product of a 

 primarily single and independent animalcule, but in the one now alluded 

 to it very frequently, though not invariably happens, that such a cyst is 

 the product of two primarily amalgamated or conjugated zooids. In certain 

 cases, even, as, for example, Heteromita uncinata, as many as three or four 

 conjugated animalcules build up the characteristic sporocyst. This special 

 sporular form of encystment is, with but few exceptions, limited to the 

 Flagellate class of the Infusoria. 



Locomotive and Prehensile Appendages. 



All of the variously modified appendages possessed by the several 

 orders of the Infusoria, used indifferently for the purposes of locomotion or 

 prehension, are to be regarded as mere extensions of the body-protoplasm ; 

 sometimes, as in most Flagellata, they are produced directly from the ex- 

 ternal surface of the ectoplasm, and in others, as the Ciliata, from the deeper 

 or cortical layer of that element. In certain Tentaculifera the characteristic 

 tentacle-like appendages would seem to originate in close proximity to the 

 central or endoplasmic region. With the exception of the organs last 

 mentioned, which would appear to most nearly represent specialized modi- 

 fications of the pseudopodia of the Radiolaria, the transition from one to 

 the other of the several types of appendages borne is most distinct and 

 gradual. In this manner, flagella can be characterized only as isolated and 

 more or less elongate cilia ; while the divers forms of setse, styles, and uncini 

 possessed most abundantly by the Ciliate section of the series, can be regarded 

 as variations only, in separate directions, of similar simple cilia. Viewed 

 from an independent standpoint, and as is requisite for the purposes of 

 technical diagnosis, the term of " cilia " may be conveniently restricted to 

 such short, slender, vibratile appendages as constitute the ordinary loco- 

 motive organs of a Paramecium, or the more or less convolute adoral ciliary 

 wreath of a Vorticella. With the name of "setae" are to be associated the 

 slender, hair- like, more or less flexible but non- vibratile appendages that 

 clothe the entire body of a Pleuronema, that are developed girdle-wise, and 

 fulfil a special leaping function in the genus Halteria, or that in an isolated 



