Introduction to Animal Morphology. 



67 



in which rod-like chitinous bodies — " teeth" — may- 

 exist (Nassula, Prorodon, &c.) There is Fig. 6. 

 usually an anus, which may be posterior, 

 anterior, or in the vestibule of the mouth. 

 The pharynx penetrates to the endosarc (or 

 endoplasma), and terminates therein some- 

 times with a valve (Glaucoma) ; the food 

 there passes round in the protoplasm, often 

 in vacuoles, and is digested. The ectosarc ^'"f!!^" .?.^J'** 



ramrecium. 



(ectoplasma) is firmer, more homogeneous, ^"' ^n'tmctiie 

 and possesses a contractile vesicle at either „. anuL'i^'^' 

 ■or both ends. These contract rhythmically, often fifty 

 times in a minute, and the fluid within is expelled 

 into the parenchyma or out by surface-pores. One 

 or many canals may be attached to this vesicle : 

 (i, Spirostomum ; 8.10, Paramsecium ; 30, Bursaria). 

 They appear to have definite walls, and are filled when 

 the vesicle contracts, or vice versa. In Stentor there 

 is a circular canal around the mouth connected wdth 

 the vesicle. The contractions of these vesicles are 

 independent of the circulatory movement of the 

 protoplasmic endosarc, which is usually active, al- 

 though the contained granules are not contractile. 



The body in Trachelius ovum '^' ''" 



(Fig. 7) consists of an endosarc of pro- 

 toplasm threads, forming irregu- 

 lar m.eshes, whose interspaces are 

 filled with water. These threads 

 functionally represent the endosarc 

 of other Infusorians, but remind us ^ 

 of Noctiluca. The ectosarc is 

 thin, and its contractile vesicle is 

 lenticular and flattened. 



The only possible sense-ors'ans Section otTrachcims ovum. 



■' ^ ^ a. mouth. 



F 2 



