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ENCYSTMENT. 63corresponding type of form with certain modifications, the areas betweenthe longitudinal ridges being transversely striate or otherwise ornamented,is common to the encystments of various Vorticellidae, while a somewhatsimilar one, having the elevated crests transversely placed, recurs in theAcinete type Podophrya fixa. In many species, such as Stylonychia pustulataand Pleurotricha lanceolata, the exterior surface of the spheroidal cystis closely studded with more or less irregular papilliform elevations. Inall these instances of simple or protective encystment, the animalcule uponthe return of favourable conditions assumes once more its normal aspect,and, breaking through the walls of its temporary prison-house, resumesits customary active habits. It is undoubtedly to the possession of thissimple self-protective faculty that the extensive distribution and prolongedvitality of many infusorial forms is mainly due. Where the ponds, ditches,or other tracts of fluid containing such animalcules become entirely dried up,these latter run no risk of extermination. Throwing out around them theirtransparent envelopes, they remain in a quiescent or torpid state until thereappearance of the previous congenial surroundings, or, taken up by thepassing breeze, are wafted away in the form of dust until conditions areencountered corresponding sufficiently with those under which they originallyflourished.The encystment of the second order to be mentioned is of comparativelyrare occurrence, and, instead of being associated with a simple conservativefunction, is an accompaniment of, or rather the prelude to, the phenomenonof multiplication by binary division, and may for this reason be mostappropriately denominated " duplicative encystment." The preliminarymanifestations and aspect of the constructed cyst correspond essentiallywith those recorded of the simply protective form but the; animalculeenclosed within its capsule, instead of resolving itself into a quiescent andinert mass, divides itself by the ordinary mode of increase by transversefission, the two halves shortly after making their exit through the wallsof the cyst, smaller in size, but in all other respects corresponding structurallywith the single pre-existing zooid. Encystment of this specialtype, in conjunction with other noteworthy data, has been observed byClaparede and Lachmann of the Holotrichous form Amphileptus meleagris.As recorded in detail later on, this animalcule is essentially predatory inits habits, and is addicted to preying upon the stationary and defencelesszooids of the Vorticellidan genus Epistylis,in the same manner that theMyxopod Vampyrella feeds upon the frustules of the Diatom Gomphonema.In a like manner also, having gorgeditself to satiety, the devouringA mphilepttis builds its cyst on the apex of the supporting stem of its latestvictim, and there undergoes the metamorphosis above described. Duplicativeencystment is recorded by Stein of Glaucoma scintillans, and in accordancewith the observations of that authority occurs also in Colpoda cucullulus,in combination with that variety of the process next described.The third, and remaining form of encystment to be enumerated, closely