THE VITAL PROPERTIES OF THE CELL 



79 



as small button-like protuberances, whilst at their free ends they 

 gradually become reduced to fine points. 



Ciliary organs may occur in large or small numbers. In the 

 latter case, when only from one to four are present, and when 

 they are generally longer and more powerful, they are called 

 flagella ; in the former case, they cover the whole surface of the 

 cell in large numbers, thousands being frequently present, they 

 are then smaller and more delicate, and are called cilia. 



a. Cells with Flagella. Flagella occur either at the anterior 

 or posterior end of the body, producing a correspondingly different 

 movement in the body. In the first case the flagella travel 

 forwards, dragging the body along after them ; in the second 

 they propel it from behind. The former mode of locomotion has 



FIG. 41. A Euglena viridis (after Stein): 71 nucleus; c contractile vacuole; o pigment- 

 spot. B Hexamitus inflatu* (after Stein). C Chilomonas puramcecium (after Biitschli) : 

 oe cytostome; v contractile vacuole; n nucleus. (From Hertwlg, Pigs. 130-132.) 



been chiefly observed in Flagellata and kindred organisms 

 (Fig. 44 A, B, C), in many kinds of Bacteria (Fig. 33 fc), in 

 antherozoids (Mosses, Ferns, Equisitaceae), and in swarrnspores, 

 under which name the reproduction bodies of many Algae and 

 Fungi are included ; the latter method of locomotion occurs in the 

 spermatozoa of most animals (Fig. 45). 



The ciliary organs of unicellular organisms have a double 



