VORTICELLA 



57 



-t.Cl. 



an 



ECTOPLASM AND ENDOPLASM 



The general character of the ectoplasm and endoplasm is the 

 same in Vorticella as in Paramecium, but the pellicle of the 

 bell-animalcule is sculptured in various ways according to the 

 species, and below it is a distinct alveolar layer so called because 

 the protoplasm appears to be full of bubble-like spaces or alveoli. 

 Just under the alveolar layer, in the walls of its bubbles, is a layer 

 of very fine contractile fibres 

 or myonemes. Near the stalk 

 the ectoplasm is much thickened 

 and the myonemes pass inwards 

 through it to join in the middle, 

 where they form a central con- 

 tractile fibre which, with a cover- 

 ing of ectoplasm, makes up the 

 stalk. This is enclosed in a 

 cuticular tube formed by secre- 

 tion. The contractile fibre is not 

 quite straight, but lies in a very 

 open spiral, so that when it con- 

 tracts it draws the stalk into a 



close coil. There are no tricho- Fig. 31. — Vorticella. highly magnified. 



cysts. The endoplasm is granular. an., Position of temporary anus ; c.f.. contractile 

 "^ JT o filament ; c.v., contractile vacuole ; cut.st., 



cuticle of the stalk; dsc, disc; ec. ecto- 

 plasm ; f.v., food vacuoles ; g., narrower 

 part of gullet ; i.ci., inner row of cilia ; meg., 

 meganucleus ; mi., micronucleus ; myn., 

 myonemes ; o.ci., outer row of cilia ; pst., 

 peristome ; res., reservoir of contractile 

 vacuole; rim; u.m., undulating membrane; 

 v., vestibule. 



meg.- 



INTERNAL ORGANS 



A meganucleus and a micro- 

 nucleus are present, the former 

 a long, curved band, the latter small and placed beside the 

 meganucleus, usually in the upper part of the body. There is a 

 contractile vacuole, which has no canals. It lies in the upper 

 region of the body and communicates with the vestibule through 

 a reservoir, which has a narrow permanent opening. The con- 

 tractile vacuole contracts sharply at intervals, discharging into 

 the reservoir. The latter then contracts slowly, driving its contents 

 into the vestibule, but not itself disappearing. Feeding and diges- 

 tion take place much as in Paramecium. The little organisms 

 which serve as food are collected and driven into the gullet by 

 the action of the cilia. The food vacuoles follow a definite, winding 

 M.z. — 3 



