290 GENERAL HISTORY OF THE INFUSORIA. 



of the genus first named is always simple or unbranched (XXVII. 1, 2, 3, 4) ; 

 but in that of the other genera of VortkeUina — viz, Carcliesmm (XXX. 9) 

 and ZootJiamnium (XY. 69) of the contractile-stalked group, and Epistylis 

 and Opercularia of those having rigid stems (XXX. 1, 11) — the young beings 

 produced by fission continue adherent to the parent stem, and then proceed to 

 develope secondary branching pedicles of theii' own, and in this manner give 

 rise to compound ramified collections of polj^^aries. Since this ramification 

 is consequent on the division of a parent-being into two, it has necessarily 

 a more or less regular dichotomous (forked) character, and will be more com- 

 pound the oftener the process of fission has been repeated. 



The stem produced by each liaK continues to acquii-e length and strength 

 until the being which surmounts it begins in its turn to undego self- division, 

 when its growth at once ceases ; and it undergoes no further change whilst it 

 exists, except in acquiring increased consistence. 



'' The individuals on the same stem have," says Steia (p. 75), '' as a rule, 

 similar dimensions, those undergoing fission, and therefore 'svider, excepted. 

 At times, indeed, one may be found smaller than its neighboui'S ; but this will 

 be traceable to some accidental cu'cumstance, such as a less supply of nu- 

 triment to it, and is never very considerable. The size of the members of the 

 same colony agrees in general with that of the individual from which the 

 whole have sprung. When the newly- developed fission-segment, after detach- 

 ing itself from its parent, forthwith proceeds to fix itself and secrete its stalk, 

 the newly-developed colony will coincide in dimensions with that from which 

 this animalcule has proceeded. On the contraiy, if the detached member 

 enjoys its freedom a longer time, appropriates nourishment, and attains a 

 larger growth, the new arborescent poljpary developed from it will be larger 

 in all respects than the parent colony. Hence it is, that in the same species 

 we have great variety in the dimensions of individual members as weU as of 

 colonies ; and therefore the height of the pedicle, the thickness of its branches, 

 and the size of its individuals are useless as specific characteristics." 



The style of ramification is equally devoid of constancy in the same species : 

 for (to continue our extracts from Stein) " the several branches may attain 

 an equal elevation, and so produce a cor^^mb or cyme ; or the inner may out- 

 grow the outer branches, and the whole polypary resemble a bunch of grapes 

 or a panicle ; or, as occasionally happens, the branches may be all incompletely 

 developed, but at the same time bear numerous individuals on short stems, 

 arranged in close series on one side, when there will be a resemblance to an 

 ear of corn." 



In the case of Ophrydium there is a considerable departure from the ordi- 

 naiy structure and arrangement of the polj^aries of VorticeUina and the rest 

 of the Ophryd'ma. Ehrenberg considered the globular masses of Oplirydium 

 to be constituted by the cohesion of their gelatinous sheaths, and to be the 

 consequence of their incomplete self- division. This, however, seems to be 

 incorrect ; for Stein (p. 246) confirms the statement of Frantzius, that the 

 gelatinous ball is not made up of coherent sheaths, but that the bodies of the 

 OpJirydia are merely attached by their tapeiing posterior extremities to its 

 surface, and not imbedded within it. The animal sends, indeed, a prolonga- 

 tion of its tapering base some short way within the homogeneous matrix, 

 like a root ; and when it forcibly contracts itself, a shght depression of the 

 surface occurs ; but in no strict sense can the gelatinous excretion be called a 

 sheath or lorica. 



Although, in their usual phase of being, the attached Ciliata have no power 

 of locomotion, they are nevertheless capable of considerable relative move- 

 ment. The highest degree of this is seen in the actively contractile stems of 



