62 



PRINCIPLES OF ANIMAL BIOLOGY 



Polished Edge 



He made an enclosure by cementing two cover glasses to the surfaces of 

 a glass slide with a polished edge, so that the cover glasses projected 

 over this edge (Fig. 27). Into this chamber amcebas were put and the 

 chamber was mounted on the stage of a horizontal microscope. In this 

 manner the amoebas could be observed from the side. Viewed thus 

 their locomotion was shown to be a sort of walking (see Fig. 28). Both 



Jennings's and Dellinger's experi- 

 ments show that protoplasm is con- 

 tractile. Attempts have been made 

 to show that amoeboid movement is 

 due to changes in surface tension 

 and many experiments have been per- 

 formed on non-living material to ex- 



Fig. 27.— Apparatus for the study of pl^in this form of movement. How- 

 locomotion in Amoeba in side view. It . 



consists of a glass slide with a polished ever, it appears that the currents .^of 

 edge and two projecting cover glasses protoplasm in Amceba do not rim'in 



which form a groove in which the speci- i i i •/• 



mens are kept. It is used on a hori- the Way they should if movement 



zontal microscope. (From Dellinger m ^^re duC tO SUrface tcusion aloue. 

 Journal of Experimental Zoology. ) » i • i 



Amoeboid movement occurs m 

 the Protozoa provided with pseudopodia, in some naked plant cells, 

 and in some cells of higher animals, namely, white blood corpuscles and 

 pigment cells. Some other cells, as the germ cells, which originate in 

 one location and migrate to another at some distance probably use 

 this form of locomotion during their migrations. 



Fig. 28. — Locomotion in Amoeba proteiis as seen from the side with the apparatus shown 

 in Fig. 2/. A and B show the extension and attachment of a slender pseudopodium. 

 Other pseudopodia are moving forward. (From photomicrographs by Dellinger in Journal 

 of Experimental Zoology.) 



Ciliary Movement. — Many small animals, such as the Infusoria of 

 which Paramecium is the best known, wheel animalcules (rotifers), free- 

 living flatworms, nemertean worms, and the aquatic larvae of many ani- 

 mals are provided with numerous cilia, covering a portion or all of the 

 surface of the body (Fig. 18). Each cilium has an elastic outer layer 

 containing one or more contractile protoplasmic elements within it. The 

 structure of a cilium of Stylonychia is shown in Fig. 29. Each large 

 ciUum of this and similar forms' is regarded as being formed of several 

 cilia of ordinary size fused together. Contraction of the protoplasmic 



