$$ 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 cesophagus, 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 
genera Difflugia and Arcella of the Rhizopoda.* 
. 2 Bursaria, Paramecium, Urostyla and Sty- 
lonychia. In Glaucoma scintillans the ciliated 
crown of the mouth is replaced by a special semi- 
Junar ciliated lobe. 
8 In Stentor, Vorticella, Epistylis and Tricho- 
dina, this apparatus is retractile, and produces in a 
particular way the vortical actions. In Spirosto- 
mum ambiguum, there is a long, narrow, ciliated 
furrow, through which the food is conducted to the 
mouth, situated at the posterior portion of the body. 
4 Prorodon, Nassula, Chilodon and Chlamido- 
don. Here the hair-lilye teeth are arranged in a 
cylinder so as to resemble a weir. 
6 The cesophagus is short in Oxytricha, Sty- 
lonychia, and Eupjotes ; but is elongated or spi- 
ral in Vorticella, Carchesium and Epistylis ; 
*[§ 15, note 1.] Kélliker ( Siebold and Kolli- 
ker’s Zeitsch. I. 1849, p. 198) has given a long and 
detailed description of Actinophrys sol. Accord- 
ing to him, it is without mouth or stomach proper, 
and internally is dof ab sub- 
while it is long and arcuate in Bursaria trunca- 
tella and cordzformis. 
6 The undigested matters accumulate about the 
anus, and when this opens are expelled from the 
parenchyma with a certain force. With Nassula 
elegans, the greater or Jess portions of the Oscil- 
latoria gracillima (K#utzing) upon which it 
feeds, and which are of a blue-green color, dis- 
solve into granules of this color. But these, dur- 
ing the process of di ion, gradually a 
brown color, and form irregular masses in the pos- 
terior portion of the body, and are from time to 
time expelled as brown foeces. These green gran- 
ules are not therefore eggs, as Ehrenberg (loc. 
cit. p. 339) has supposed. This Nassufa when 
young is perfectly colorless, with the exception of 
a beautiful blue spot. 
stance. Yet this remarkable animal lives on other 
Infusoria, Algae, &c., and avails itself of them by 
seizing and afterwards invaginating them in its pa- 
renchyma, until they finally are included within ita 
interior. — Ep. 
