OF THE PROTOZOA. CILIATA. 6fO 



life instantly. Cyanide of potassium did the same, producing at the same 

 moment ruptui-e of the integument and the discharge of the contents. On 

 adding a quantity of oxalate of ammonia to the water, a stupefying effect at 

 once follows, but after a few minutes the animalcules revive, and death does 

 not result — at least, not for some hours. Likewise, neither ferrocyanide of 

 potassium nor neutral chromate of potash kills — at least, not under several 

 hours. This last-named fact suggests the possibility of chemically injecting 

 or impregnating animalcules, whilst stiU Living, with a mixtm^e of suitable 

 reagents to produce coloured precipitates which might serve in demonstrating 

 their internal structiu'e. 



Geographical Distribution. — We know as yet of no special laws of geo- 

 (jrapliical distribution of the Ciliated Protozoa ; and a long time must, we 

 fear, elapse ere the waters of the earth are sufficiently explored to warrant 

 even an approximative sketch of such laws. Wherever on this globe we 

 may seek for these animalcules, they are, it seems, to be found — even the 

 same families, genera, and species ; and if our present knowledge leads us to 

 define particular localities for particular sj)ecies, it amounts to little more 

 than stating that they have there arrested the attention of some observer or 

 observers, and have been overlooked or searched for at the wrong season, or 

 under unfavourable circumstances, in other places. Por, as our remarks on 

 the succession of species imply, the animalcules present in any collection of 

 water one week, may be in vain searched for the next ; and the inhabitants 

 of a pool or stream of one season, or of one year, may be exchanged for 

 others the next. Although, therefore, laws of geographical distribution 

 are wanting, yet we may be very much guided in our search for particular 

 genera and species by a knowledge of their habitats and of the conditions 

 which prove most favourable to their existence. 



Since the whole framework of CiKata is sooner or later destructible by 

 diffluence, their occurrence in a fossil condition is not to be looked for. 



Affinities of the Ciliated Protozoa with other Animals. — Eegarding 

 as we do the organization of Ciliated Protozoa as belonging to a type sui 

 generis, their affinities with other animals partake rather of a general than 

 of a particular character. They possess an affinity with Rhizopoda, Gre- 

 garinida, and Spongilla, with Opalinceay Polypes, and with many Phytozoa, 

 such as Euglence, in the nature of their contractile substances or sarcode ; 

 also with the first and last-named, in the presence of one or more contractile 

 vesicles. Multiplication by fission is also common to those several tribes, and 

 that by gemmation to Vorticellina, Oplirydina, and Polypes ; lastly, they 

 agree with the Ehizopoda and Polycystina in the process of dissolution by 

 diffluence. In the process of encysting, also, they are related with the Opa- 

 lincea and Phytozoa, with some, at least, of the Rhizopoda, and, in general 

 characters, with the Gregarinida. 



Of the mutual relations between the Ciliata {Opalincea, Gregarinida) and 

 Rhizopoda, we shall have further occasion to speak. But the Ciliata are 

 also allied to the Rotifera by the chitinous constitution of their integument, 

 by being moved chiefly by cilia, and more closely so through certain fanulies, 

 e. g. the Vorticellina and Ophrydina, which have a frontal ciliary mechanism 

 approaching in structure that of the rotary apparatus. So, again, in some 

 general features, the sheathed Ophrydina (e. g. Vaginicola) may be assimi- 

 lated with the encased Rotatoria, such as (Ecistes and ConocJiihis. Lastly, 

 by means of the Ichthydina an additional link is established between these 

 two classes, and also betAveen them and the TurheUaria ; for some, as Schultze 

 (MiiUer's Archiv, 1853, p. 241), seem disposed to range the Ichthydina with 

 the last-named family. A homology may be perceived between the hardened 



