RHIZOPODS. 115 



g. Shell usually brown, sometimes colorless (A). 



g. Shell colorless, ovoid, not curved (/). 



g. Shell often yellowish, retort-shaped, neck curved, 

 mouth downward, circular. CyphodMa, 11. 



h. Circular, depressed, with or without marginal 

 teeth. Arce'lla, 8. 



i. Mouth oblique, circular, not serrated; shell in- 

 clined, without spines. Trine'ma, 9. 



i. Mouth serrated, not oblique; shell not inclined, 

 formed of hexagonal or rounded plates; often 

 spinous. Eilglypha, 10. 



I. Amceba (Fig. 92). 



There is hardly a living animal so soft and change- 

 able in shape as this. It may not retain the same form 

 for a second at a time. The soft body protrudes thick, 

 blunt, finger-like pseudopodia from any part of its sur- 

 face, but usually from the front margin, or that edge 

 which at the time happens to be the forward part of the 

 moving creature. The front may, with scarcely a 

 warning, become the rear as the animal changes- its 

 course, by emitting pseudopodia from some other por- 

 tion, and travelling off in the direction towards which 

 they extend. The semi-fluid contents of the body are 

 colorless, unless tinged by the food or by the presence 

 of numerous dark particles. 



The movements are sometimes rapid, the Amoeba 

 protruding its pseudopodia, keeping them extended in 

 advance, and gliding along as though the body were 

 formed of the white of egg. In the figure the 

 animal is shown in what may be considered one of its 

 favorite attitudes as it resembles one frequently as- 

 sumed ; yet it is not possible to present a typical figure 



