210 GENERAL HISTORY OF THE INFUSORIA. 



the case of the silicious- enveloped Diatomece, the dense skeleton, emptied 

 of its organic contents, continues visible for a longer or shorter time. The 

 robbing of the frustules of Bacillaria, and the appropriation of their coloured 

 endochrome, has been referred to in the foregoing remarks on the colouring of 

 Rhizopoda (p. 203) by the green colouring-matter of plants. 



The Rhizopods Bailey describes were met with in a vivarium, into which 

 " bits of boiled beans and potatoes had occasionally been introduced as food 

 for other animalcules ; .... on the application of tincture of iodine to these 

 animals, a distinct blue colour was often seen diifused over the whole surface 

 of many of the grains of sand in their stomach." 



The above facts — to which we may add another, viz. that the abimdance of 

 granules in the interior is in direct proportion with that of food — furnish 

 sufficient proof of the occurrence of a digestive faculty, and of a power of 

 assimilation among the Ehizopods. This imphes the existence both of a 

 digestive fluid, and of a secretory fimction ; the latter, too, is further ex- 

 emplified by the production of shells in the majority of the class. 



Auerbach (op. cit. p. 422) distinguishes two leading varieties of granules in 

 Amoehce : — one of a pale colour and finely di^dded, and either soluble in 

 alkalies and acids, and tui'ned brown by iodine, or, more rarely, insoluble in 

 alkalies ; the other, dark in hue, strongly refracting, and usually corre- 

 spondent in number and relative size with the animalcules to which they 

 appertain. These latter have the aspect of fat-molecules ; are spherical or 

 elliptic, or at times crystallized in a rhombic form ; and they are easily soluble 

 in cold alkaline solutions, and more slowly so in concentrated acetic and sul- 

 phuric acids. In one species, A. bilimhosa, he met with starch globules ; but 

 these were probably of extraneous origin. 



Movements of contained particles. — Every movement of the mucous sub- 

 stance of Khizopoda is accompanied by one of the granules, and of the small 

 vesicles or globules contained within it. This motion of the contents follows 

 a certain course, and is especially observable in the outstretched variable pro- 

 cesses. Schultze thus describes it in the large Amoehctpor recta : — '' A continued 

 current of the granules, imbedded in the contractile substance, accompanies all 

 these phenomena {yiz. of polymorphism) ; and, in the processes, this cuiTcnt 

 follows two directions ; thus the globules may be seen advancing on one side, 

 towards the end of the process, when they turn round to the other, and are 

 carried Tvith a comparatively more rapid motion back towards the base of the 

 filament, where they are lost in the substance of the body, unless they happen 

 to meet another stronger stream by which they are reconveyed through the 

 same circuit." A precisely similar phenomenon is witnessed in the testaceous 

 E-hizopods. Thus in Gromia oviformis, Schultze says, the granules are seen 

 to depart from the substance within the shell to the end of the filaments, and 

 thence to retui^n again to the point from which they set out. This circula- 

 tion goes on in every process ; but it is in the broader filaments, containing 

 numerous granules, that the double stream is chiefly visible : for in the finer 

 ones, whose diameter is often less than that of some of the corpuscles, it is 

 more rarely seen ; in fact, in the latter the granules seem not to be included 

 within the substance, but to be transported on the surface. Oftentimes a 

 corpuscle, on arriving at a point where a fibre bifiii'catcs, is arrested for a 

 time, until di^awn into one or other current, — whilst at the bridge-like con- 

 nexions between adjoining filaments, where the granules pass across from 

 one to the other, it not unfrequently happens that they are transferred from 

 a centrifugal to a centripetal stream, and are consequently turned back again 

 towards the body. Moreover, in the broader processes, granules are observed 

 to come to a stand, to oscillate for a time, and at length to take a retrograde 



