^-^t 15, 16. INFUSORIA AND RHIZOPODA. 29 



§15. 



The round or elongated oval mouth of Infusoria varies as to its posi- 

 tion. Sometimes it is in front, sometimes behind ; and in some cases, near 

 the middle third of the body. Rarely naked,''' its borders are generally 

 ciliated,*^' and often its circumference is provided with a very remarkable 

 ciliary apparatus. By the aid of this, these animals not only move about, 

 but when quiet produce vortical actions of the water, which are felt at 

 quite a distance; and all minute particles within its reach are quickly 

 drawn towards its mouth, and then swallowed or rejected according to the 

 option of the individual.'^' 



It is rare that this oral aperture is provided with a dental apparatus.''** 

 The oral cavity, generally infundibuliform, extends into a longer or 

 shorter, straight or curved oesophagus, which is lined throughout by a very 

 delicate ciliated epithelium.'^' 



The anus, situated usually upon the dorsal surface of the posterior por- 

 tion of the body, is sometimes, though rarely, indicated by a slight exter- 

 nal projection.'"' 



CHAPTERS VI. AND VII. 



CIRCULATORY AND RESPIRATORY SYSTEMS. 



§ 16. 



A vascular system entirely distinct by closed walls from the other 

 organs is not found in the Protozoa. But with very many (with all the 

 Stomatoda, without exception) there are contractile pulsatory cavities, the 

 form, number and arrangement of which is quite varied. 



They are situated in the denser and outer layers of the parenchyma of 

 the body, and during the diastole they become swollen by a clear, trans- 

 parent, colorless liquid, which, during the systole, entirely disappears. 



1 Actinophrys. The mouth is naked also in the while it is long and arcuate in Bursaria trunca- 

 genera Diffliig^ia and Arcella of the Rhizopoda.* tetla and cordtformis. 



2 Bursaria, ParamcBcium, Uroslyla and Sty- « The undigested matters accumulate about the 

 lonychia. In Glaucoma scintiUans the ciliated anus, and when this opens are expelled from the 

 crown of the mouth is replaced by a special semi- parenchyma with a certain force. With Nnssula 

 lunar ciliated lobe. elegans, the greater or less portions of the Oscil- 



^ In Stentor, Forticetla, Epistylis und Tricko- latoria graciltima {Kulzing) upon which it 



dina, this apparatus is retractile, and produces in a feeds, and which are of a blue-green color, dis- 



particular way the vortical actions. In Sjiirosto- solve into granules of this color. But these, dur- 



mum ambiguuin, there is a long, narrow, ciliated ing the process of digestion, gradually assume a 



furrow, through which the food is conducted to the brown color, and form irregular masses in the pos- 



mouth, situated at the posterior portion of the body, terior portion of the body, and are from time to 



< Prorodon, Nassu/a, Chilodon and Chlamido- time expelled as brown foeees. These green gran- 

 don. Here the hair-lil1(3 teeth are arranged in a ules are not therefore eggs, as Ehrenberg ( loc. 

 cylinder so as to resemble a weir. cit. p. 339) has supposed. This Nassula when 



6 The oesophagus is short in Oxytricha, Sty- young is perfectly colorless, with the exception of 



lonychia, and Euplotes ; but is elongated or spl- a beautiful blue spot. 

 ral in Forticella, Carchesium and Epistylis ; 



* r § 15, note l-l Källiker (Siebold And Kolli- stance. Yet this remarkable animal lives on other 



ker''s Zeitsch. 1. 1849, p. 198) has given a long and Infusoria, Algae, &c., and avails itself of them by 



detailed description of Actinophrys sol. Accord- seizing and afterwards invaginating them in its pa- 



ing to him, it is without mouth or stomach proper, renchyma, until they finally are included within ita 



and internally is composed of a homogeneous sub- interior. — Ed. 



3* 



