OF THE PKOTOZOA. CILIATA. 281 



specimens of this animalcule, death ensued ; but before this happened, a deli- 

 cate membrane was seen to elevate itself at parts of the surface, producing a 

 vesicular appearance, and accompanied by a shrinking of the contained matters ; 

 while these changes proceeded, several contiguous vesicles would run into one, 

 and thus strip more or less completely the subjacent tissue, until, by the pro- 

 longed action of the alcohol, a central shrunken mass appeared, surrounded by 

 a loose membrane, adherent to it only at the spot where the mouth was con- 

 tinued inwards as a pharynx. This membrane, so demonstrated, is homoge- 

 neous and transparent, but not entirely structui^eless ; for close observation 

 reveals, over its entire surface, two series of spirally-disposed, delicate, and 

 closely-approximated lines, which so intersect one another as to produce a 

 miniature diamond pattern (XXIX. 26). Further, the notched or serrated 

 appearance of the periphery (XXIX. 28, 29, 30) shows that these lines are 

 actually folds or fiuTOWs, and that each little chamond may be represented as 

 a minute four- sided pyramid bearing a cihum at its summit. 



By piu'suing a similar plan of investigation, a separable integument has 

 been demonstrated in many Ciliata. For instance, Stein described such a 

 covering in the several genera he subjected to observation, and proves its ex- 

 istence also after the process of encysting has taken place. On adding dilute 

 acetic acid to the VorticelUna — for example, to specimens of Epistylis or Oper- 

 culcuia — the contents shrink into a denser mass, and in so doing detach them- 

 selves from the integument, which is then rendered evident as a transparent, 

 structureless, homogeneous, and smooth membrane, having a clear, shai-p out- 

 line. When tincture of iodine is applied, the integument remains uncoloiu-ed, 

 whilst the contents acquire a golden-yellow tint. A solution of sugar, and 

 afterwards a drop of concentrated sulphuiic acid, being used, causes the con- 

 tents to swell up and to assume a rose-red colour, the external wall continuing 

 uncoloiu^ed. 



Eespecting the chemical constitution of the membrane of Loxodes, Cohn 

 informs us it is soluble neither in sulphimc acid nor in potassa, whilst the con- 

 tents are dissolved and dispersed by the latter. From this reaction he con- 

 cludes that the cuticle is not a proteine compound, hke animal membrane in 

 general, but the substance called chitine, and therefore in this respect similar 

 to the cuticle orplants. In Parmnecmm, he adds, an integument having the 

 same sort of markings and a similar chemical reaction exists, and that, with- 

 out doubt, aU the species described by Dujardin as having a reticulated 

 envelope, in his families ^ Bui'sariens ' and ' Parameciens,' have a hke structure. 

 Moreover, this sldn has its special characters in different genera, as is illus- 

 trated in the above accoimt of Paramecium Bursaria, and may be exemplified 

 in other cases. Thus in Coleps and Stentor polymorphus, the cuticle is so 

 intersected by lines as to leave intermediate four-sided prisms, each of which 

 bears a cihum at its apex, whilst at the intersection of the lines, single long 

 hairs are also seen, similar, says Lachmann {A. N. H. 1857, xix. p. 1 2b, in foot- 

 note), to the hairs of many TnrheUaria. Again, Ophrydium versatile has its 

 integument thrown into fine, closely-aggregated, annular folds, and into three 

 longitudinal rugae on one side (XXX. 5), which disappear when the animal 

 shortens itself by contraction (XXX. 6). Spirochona (XXX. 17), says Stein 

 (p. 208), has a hyaline, firm, inflexible parchment-Hke sldn, with a distinct 

 double outline, but mthout any inherent contractility. It is most like the 

 integument of Euplotes, but differs apparently in not being capable of falhng 

 into folds around the body. It resists the action of acetic acid, which dis- 

 solves out the whole of the Hving contents, and leaves it in an isolated state. 



Whilst representing all animalcules to be covered with an integument, 

 Ehrenberg distinguished those enclosed by a firm, more or less unyielding, 



