250 GENERAL HISTORY OF THE INFUSORIA. 



noticed consisted of a Lynceus and a young Cyclops. Eichhorn, indeed, 

 mentions a water-flea {Daplinia ?), about the size of which, however, no re- 

 mark is made." Indeed, the Actinophryina are rapacious animals, and will 

 appropriate to themselves any organisms, vegetable or animal, which fall in 

 their way. Thus, besides those beings alluded to already, Eotifera, various 

 minute Crustacea, Cihated Protozoa, Phytozoa of all sorts, Desmidieae, Dia- 

 tomeae, minute Algae, and their spores ahke fall a prey to these remarkable 

 animalcules. The excrementitious particles of food, as already stated, pass 

 out at any spot where circumstances may dii-ect them ; and no definite anal 

 aperture, such as Ehrenberg imagined, has an existence. The expulsion of re- 

 sidual matters, Mr. "Weston {J. M. S. 1856, p. 121) states he has " fi'equently 

 seen, — in one specimen twice in less than half an hour, at diiferent spots. In 

 watching the digestion of a Rotifer, it occurred to me to see a dark body, 

 composed apparently of the case, remain for some hours in the same spot, 

 and then gradually approach the side, as if for expulsion ; but while waiting 

 for this to take place, an opening in another part occuiTed, and excrement 

 was voided in quantity : this voided matter lies amongst the bases of the 

 tentacles, while the opening through which it has passed closes ; and then, 

 with the same stealthy motion I have before described, it is apparently diiven 

 along the tentacles (as if by repulsion) beyond their extremities, finally dis- 

 appearing in the surrounding medium." 



Contractile vesicle. — The rule is, that only one contractile vesicle belongs 

 to each animalcule (XXIII. 36, 37). If more appear, it usually indicates 

 either the approach of fission, or the conjugation of two or more individuals 

 (XXIII. 33-35). Kolliker failed to recognize this organ in Actinophrys, and 

 concluded that Siebold had described as such the mere changeable vacuola. 

 However, Stein, Claparede, Cienkowsky, and others concur in representing a 

 contractile vesicle as normally present ; the fii'st-named writer, indeed, de- 

 scribes in a few instances two such, as Siebold has done before him. Stein 

 exhibits, in Actinophrys Sol, the vesicle as central (XXIII. 1) ; but other 

 naturahsts concur in representing it as supei-ficial, — so much so, according to 

 Siebold, that it will frequently dming its expansion project above the general 

 surface, and thereby prove itself to have a distinct wall (XXIII. 29 m) ; for 

 if composed of only the gelatinous parenchyma of the body, it would burst at 

 the moment of greatest expansion. It is, therefore, a closed sac or cell. 

 Claparede has never found more than one vesicle, and thinks both Siebold 

 and Stein in error in describing two. " Several vesicular elevations," he 

 writes, " often occur on the margin ; but only one of these is contractile. I 

 have, however, observed two contractile vesicles in several individuals ; but 

 in these cases the form always gives rise to a suspicion of fission, or of an 

 amalgamation of two individuals (Act. clifformis, Ehr.). The presence of a 

 single contractile vesicle does not, however, appear to be imiversal among the 

 Rhizopoda ; I have observed two in Arcella vulgaris .... It is surprising that 

 Kolliker, who was acquainted with Siebold's observations, should have cha- 

 racterized them as inexact, and as arising fi'om an illusion. According to 

 him, Siebold had mistaken accidental expansions and contractions of the sub- 

 stance enclosing the vacuoles, in which the latter were persistent, for phe- 

 nomena indicating the existence of contractile reservoirs. This, however, is 

 not the case ; the size, the unchanging position, and the regular expansion 

 and contraction of this organ will prevent its being confounded with a 

 vacuole. That KoUiker should have overlooked it is particularly iminteUigi- 

 ble, as the phenomenon is immediately presented by nine out of ten specimens 

 of Actinophrys.''^ 



Carter {A. N. H. xviii. p. 129) makes the curious assertion, that the '^Actino- 



