280 GENERAL HISTORY OF THE INFUSORIA. 



contractility and elasticity, and is the active agent in the movements of their 

 bodies. It is hyaline, transparent, and colomiess ; but its refractive power 

 is not much greater than water, which is essential to the exhibition and 

 continuance of its properties, for when this fails the homogeneous mass of 

 sarcode breaks up into minute globular portions, which disperse themselves 

 on every side. This disruptive process has received the appropriate name, 

 from Dujardin, of ' diffluence.' 



Ecker states this self-same sarcode to be the common contractile element 

 of all the lowest forms of animal life — for instance, of the Polypes. The par- 

 ticles set free by ' diffluence/ he also represents to be contractile, and to 

 assume Amceba-like movements ; but this, according to Gohn and Stein, is 

 an error, inasmuch as they are simply elastic. Cohn also adds that the 

 vaiiable movements of the sarcode-particles of Hydra are merely a physical 

 phenomenon due to endosmosis. The process of diffluence, whether fi'om 

 external injiuious conditions or damage, or from noxious matters received 

 ^vithin, varies so much in rapidity, that Cohn (Zeitschr. 1851, iii. p. 267) con- 

 eludes that it must indicate some variations in its composition and stnicture 

 in different animalcules. For instance, he says, Steator ccertdeus bursts ; and 

 its contents break down by diffluence as rapidly as sugar in water, streaming- 

 out from the rest until the fimnel-like pharynx only is left behind. On the 

 contrary, in other animalcules, e. g. Paramecium Aurelia, the sarcode exudes 

 through the surface at all points, and s^dms away, lea\ing a vacuolated or 

 areolated interior. Again, Loxodes breaks up into fragments of a considerable 

 size, which escape through lacerations of the sui'fiice. 



Integument. Markings on the Surface. Condensed Integument or 

 LoRiCA. Appendages of Integument. Cilia. Spines. External Sheaths. 

 -— Ehrenberg described his Polygastrica as in all cases defended, and their 

 figure defined, by an integument or skin, — a statement as g-eneraUy contra- 

 dicted by Dujardin, though now confirmed (in the case of all the true Ciliated 

 Protozoa) by the researches of numerous later naturalists. The means resorted 

 to for its demonstration, where not otherwise e\ddent, consist in the application 

 of chemical agents — for example, of acetic acid, of tincture of iodine, and of 

 diluted alcohol, aU which operate in a different maimer upon the integument 

 and on the contents of the body, most frequently causing a separation of the 

 two by corrugating the latter, and, it may be, coloimng it at the same time. 



Perty could not convince himself of the existence of an epidermis, although 

 he believed the external surface to be modified so far as to render it more 

 resistant, or in fact to form what Mr. Carter calls a pelKcle ; at the same time 

 he attributed marks or lines visible on the surface to fat- or other corpuscles 

 subjacent to it. '^The pellicula," Mr. Carter says, '^is a structureless pro- 

 duct, which hardens after secretion ; and the inference is that there is a layer 

 below specially organized for its formation," and that it is not secreted by 

 the lamina known as the " cortical layer " or the '' diaphane." 



On the other hand Meyen, Siebold, Kolliker, Erey, and Leuckart conciu- 

 in describing a distinct enveloping delicate membrane, which Erey thought 

 evidenced both by the manner in which an animalcule ruptures under pressure 

 and gives vent to the soft contents, and by the appearance of little shreds he 

 noticed on the torn edges of a Stentor. A more direct demonstration was 

 afforded by Cohn, who resorted to chemical reagents for the purpose. 



This excellent observer experimented with several of the larger Ciliata, but for 

 illustration referred chiefly to Lo.vodes (Paramecium) Bursar ia. Stein argues 

 that the animalcule so described by Cohn was not a Loxodes, but a Paramecium, 

 .since aU its cilia were of equal length, a feature pecidiar to this genus (Stein, 

 op. cit. p. 239). On adding a little alcohol to a drop of water containing 



