OF THE PROTOZOA. CILIATA. 303 



wliich, as forming a tube distinct from the parenchyma of the body, and 

 hanging freely in the ahmentary cavity, is perhaps entirely wanting in some 

 species ; at least, I have hitherto been unable to detect it in Amrph'deptus, 

 most species of Trachelius, EncJielys, Coleps, and Trachelocerca, in which it 

 only appeared to be a canal through the parenchyma of the body : and these 

 are generally incapable of forming roundish morsels like the species hitherto 

 imder consideration ; but they usually swallow larger particles, which then 

 pass separately into the cavity of the body, often even without being accom- 

 panied by water. It is very difficult to determine whether the oesophagus of 

 these animals is furnished internally with cilia. In some, such as Coleps, 

 this almost appears to be the case : these STvdm to any slimy mass, such as a 

 dehquescent Infusorium, press the anterior extremity of the body against it, 

 and open the mouth and oesophagus, which are usually closed, so as to form 

 a wide canal ; the mass lying before the Coleps then j)asses through this canal 

 into the interior of its body, apparently without any swallowing movements 

 on its part, so that it can hardly be diiven in except by ciliary action. In 

 others, on the contrary, the cilia of the oesophagus appear to be wanting, as 

 in Ampliileptus, Enchelys, Trachelius ; these perform regular movements of 

 deglutition, in order to overcome their prey, which usually consists of Infu- 

 soria of tolerable size : they push themselves, as it were, with swallowing 

 motions, like the Snakes, over their prey (so that they can very rarely be fed 

 with colour) ; and this never forms stomach-like morsels, except when it is 

 contained in this form in the Infusoria devoured." 



Sto:mach-sacs. The Polygasteic Hypothesis. — The next organs, con- 

 cerned with digestion, to be considered, are the stomach-sacs or vesicles of 

 Ehrenberg— the "digestive globules" of Mi\ Carter (XXYIII. 8/). The 

 former has described these to be disposed after certain definite types, which 

 fonn the basis of his system of classification of the Polygastinca. To describe 

 these t}^es, we must premise that the families comprised in our group of 

 Ciliated Protozoa represent the Enterodela of the Berlin naturalist, or those 

 Polycjastrica having a true alimentary canal uniting the stomach-sacs together, 

 and continuous throughout from the mouth to the assumed discharging orifice. 

 The Entei^ocMa were subdivided into sections according to the relative posi- 

 tions of the mouth and anus. The first of these was named Anop'istliia, in 

 which the intestine was so ciuwed upon itself that its two extremities were 

 contei-minous in one aperture, which therefore ser\'ed the double office of a 

 receiving- and a discharging- orifice. This curvature of the intestine further 

 suggested the term Cyclocoela to express it. The families in this section were 

 Vorticellina and Ophrydina. The next section, called Enantiotreta, included 

 animalcules in which the oral and the anal apertin-es were at opposite ends of 

 the body. "VMien this was the case, the intestine might either pass straight 

 between the openings, or be more or less twisted in its course : in the former 

 ease, the Polyyastrica were called Ortliocoela ; in the latter, Campylocoela. 

 The EncJielia and Colepina were the two families of Enantiotreta. The third 

 section was the AUotreta, having one orifice terminal, and the other lateral, 

 and the fourth the Catotreta, having the two orifices on the same side, not 

 terminal but abdominal. The members of these two last sections, lastly, had 

 either a straight or, more commonly, a contorted intestine, or, in other words, 

 were either Orthocoela or Campyloccela. 



^ Such is an outhne of Ehi'enberg's views of the alimentary apparatus of the 

 Ciliated Protozoa, as advanced in his great work of 1838, and never since re- 

 called. They rested chiefiy on some imperfect obsei-vations and experiments 

 made with coloured food, and have failed to be confirmed in the hands of 

 other mieroscopists. Although diligently sought after, no one has been able 



