184 THE AMHltKWX MONTHLY l.Tuly, 



Althoujih 1 liavo not actually sin-ii luiiiut*' slrcams issiiin«r 

 from tlu> extriMiuty of each villus, tlu'iv can l)o hut little douht 

 that stroaius (K> so issuo. If tiu' limitinu' imMuliraiit' is picnctl 

 by aperlurt'S they must he inlinitely iuor«- miiinti* th:m arc the 

 stvontlary apertures in any known «liatoni ; and the proper eon- 

 (litit)ns for (lenu>nstratin.>: the perforations, if they exist, eannot 

 he made, as they can he made with a diatom ; yet the sudden 

 protrusion of the nipple-like processes with the hypothetical 

 aperture at the extremity of each, i^ i)recisely what reason would 

 sujrjiesi as the result of the rai)id movement of a crihril'orm vi'S- 

 ide, the enclosed tiuid heinj: restrained in the rear hy the re- 

 sistinj; hody-suhstance. The amount of li(|uid in the vacuole 

 is small, and although, the internal force that protrudes the villi 

 seems, under the microscope, to he comparatively ^'reat, it must 

 of course he cxceedinLdy slijrht. Yet it is ureat enouLih to pro- 

 duce a surprising: chancre in the a]>]>ea ranee of tiie external sur- 

 face. 



D'\ Lfidy, speaking of the contractile vesicle of Artin(ii>/iri//i 

 Si I, says: '" Gradually expandinjr, it rises as a film of granular 

 protoplasm, which, hecominir thinner and thinner, finally hursts 

 and f^ives exit to the liquid contents." In reference to the two 

 vacuoles of Adinnxph.Trium eic/ihoniii he says : "On reachin<,f the 

 lull degree of expansion, they rather ahruptly collapse, and ex- 

 ])el the liquid contents." And the new edition of "Carpenter," 

 referrinj; to the contractile vesicle of Actimqilrryx, says: " The 

 cavity of this saculus is not closed externally, hut communi- 

 cates with the surroundim^ medium, — not, however, hy any dis- 

 tinct and permanent orifice, the memhraniform wall jrivinj^ way 

 when the vesicle contracts, and then closing over again." 



The vesicles oi' Actino])hrys do not hurst. From what I have 

 repeatedly observed and have here described, 1 am convinced 

 that there is no such action. If rujtture actually took place, it 

 could be reailily seen, since the vesi(;lc is large; in Actiiiosphx- 

 rium eichhornii it should be noted with much greater ease as the 

 organs are there still larger. But what does take i)lace is the 

 sudden i)rotrusion of the nipple-like processes, with apparently 

 the forcible ejection of the vacuole's licpiid contents through 

 them. 



With the Infu.soria it is not always possible to demonstrate 

 the existence of a passage from the contractile vesicle to the 



