192 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



Order Peritrichida 



The spectacular contractility of peritrich ciliates has earned 

 them repeated notice, but little as yet in the way of concerted 

 study, from biologists interested in the chemistry and physics of 

 protoplasmic contraction. The cell body of the peritrich is 

 commonly goblet- or bell-shaped. The flat upper or oral surface 

 consists of a disc usually called the peristome, bearing peripherally 

 two or three parallel, spiral rows of cilia that lead via a more or 

 less profound canal, the infundibulum or buccal cavity proper, 

 to the cytostome. The aboral region bears a girdle of locomotor 

 cilia called the trochal band in motile species and in migrant 

 individuals ; in adults of sessile species an aboral polar area called 

 the scopula produces an adhesive substance, often forming a long 

 stalk that encloses a myoneme in some species. 



Rapid protoplasmic contraction is observable in several parts 

 of the body: a protoplasmic collar around the peristome may 

 constrict to enclose peristome and its cilia; the body itself may 

 contract into a tight ball; a basal disc in creeping motile species 

 may contract, and finally and most flamboyantly, the long stalk 

 may contract abruptly into a tight coil. The latter is true only of 

 some genera; others have non-contractile stalks. The myonemes 

 observable in stalk and body by light microscopy color intensely 

 with protein stains and are optically anisotropic, showing the 

 same alterations on contractions as metazoan muscles (Faure- 

 Fremiet, Rouiller, and Gauchery, 1956b). Myosin- like proteins 

 have not been demonstrated in them. Levine (1960) has shown 

 specific ATP-ase activity in the stalk and body myonemes of 

 Vorticella. But stalk models differ from muscle in details of their 

 response to ATP (Hoffmann-Berling, 1958a, b). 



Recovery from contraction requires an antagonistic system of 

 some kind, and the peritrichs appear to be provided with elastic 

 skeletal structures that serve this purpose. 



Comparison of the ultrastructure of contractile and non- 

 contractile peritrich stalks provides a basis for unassailable 

 identification of myonemes versus supportive elements. Pertinent 

 information comes from the work of Faure-Fremiet, Rouiller, and 

 Gauchery (1956b), Randall (1956, 1959a, 1959c), Rouiller, 

 Faure-Fremiet, and Gauchery (1956a, 1956c), and Sotelo and 



