24 INFUSORIA AND RUIZOPODA. *§*>§. G, 7, 8. 



C H A P T E n I . 



EXTERNAL COVERING. 



§6. 



The Protozoa are surrounded by a very delicate cutaneous envelope, 

 which is sometimes smooth/* and sometimes covered with thielcly-set cilia.'-' 

 Generally these cilia are arranged in longitudinal rows ; •'" but in Actiiio- 

 phrys they consist of long contractile filaments of a special nature. 



CHAPTER II. 



muscular system and locomotive organs. 



With the Protozoa a distinct muscular tissue cannot be made out, but 

 the gelatinous substance of their body is throughout contractile. 



It is only in the contractile peduncle of certain Vorticellina, that there 

 can be perceived a distinct longitudinal muscle, which, assuming a spiral 

 form, can contract suddenly like a spring.'^' 



§8. 



The Vibratile Organs on the surface of Infusoina serve as organs of 

 locomotion. 



With many species they are found much developed at certain points, 

 and are arranged in a remarkable order and manner. 



With Peridinium, a crown of them encircles the body ; with Stylony- 

 chia, they are quite long, and surround the flattened body like a fringe ; 

 while the Vorticellina have the anterior portion of their body surrounded 

 by retractile cilia, arranged in a circular or spiral manner. In Trichodina 

 tiiere is, upon the ventral surface, besides a crown of these cilia upon the 

 back, a very delicate ciliated membranous boi-der, which is attached to a 

 ring which is dentated, and composed of a compact homogeneous tissue. 

 With Trichodina pedicidiis this border is whole and entire; but it is 

 broken or ragged with Trichodina mitra.^^' 



By means of this organ these animals swim with facility, or invade with 

 skill the arm-polyps and Planaria.'-' With many Infusoria, the vibratile 

 organs are situated at the anterior extremity of the body, as simple or 

 double non-retractile filaments, which move in a manner to produce a vor- 



1 Euglena, Amoeba, (fC. i This Infusorium was UiscovcrcJ by me as a 



- Traclitlius, Faramwcium. Nassula, fyc. parasite in many Planarieae. 



•* Amphileptus, Chi/odun, Opalina, <^c. 2 Ehrcntier^ has entirfly overlooked the ciliated 



1 The peduncle is simple with Forticelia, but border (jf TricAofZ/na ;<ki(C!(/u«, and h:is regarded 



ramified with Carchcsium. With Epistylis it is the stiff serrations of the ring as movable liooks. 



not muscular. See " Die InfusionsthiercUcu," p. 206. 



