14 



ZOOLOGY 



bers on the surface of tlie sea, and is large enough to be 

 seen with the naked eye. 



The true Infusoria arc coTcrcd with cilia, or hair-like 

 processes, by wliicli tlicy glide about over submerged leaves, 

 etc. One of tlie largest and commonest Infusorians is Pa- 

 ramecium. 



Fig. 10 rejtvesenis Paramecium caiidnfiim. This animal- 

 cule is a mass of protoplasm, representing a single cell 

 In the body-mass are excavated a moutli and a throat lead- 

 ing to a so-called stomach or digestive cavity. Two hollows 

 in the body form the contractile vesicles, and anotlier cavity 

 constitutes the nucleus (n). 



The trumpet-animalcule {Sfenfor) is large enough to be 



cZ ^ 



Fig. 11. — Process of fission in Sienfor polr/morphus. ?>, a new Stentor budding 

 out; e, ready to separate from the original one; /, tlie two in a eontractea 

 state. 



detected witli the unaided eye. Tliis Infusoi'ian attaches 

 itself at one end by a stalk, and builds up a sliglit tube, into 

 wliich it contracts when disturlicd. 1'lie Stcntor may be 

 sometimes observed multiplying by self-division. 



In Sfenfor pol ijmorpli us the process of self-division takes 

 place in two hours. Fig. 11, /, rejiresents tlie final stage 

 when the two individuals swim away separately, each as- 

 suming the original adult form, a. 



The bell-aiiimalcnles, Vorficcfla and Pj)isfi/Iis (Fig. 12), 

 form patches like white mould on aquatic plants. Their 

 motions as they suddenly contract and shoot out their bells 

 is exceedingly interesting. 



Many Infusorians, besides self-dividing, produce ciliated 



