110 MICROSCOPY FOR BEGINNERS. 



d. Kays flexible, not forked. Actinophrys, 4, or 



Actinosphcerium, 5. 



e. Shell formed apparently of sand-grains (/). 

 e. Shell not formed of sand-grains (g). 



e. Shell a latticed globe on a long stem. Clathru- 



lina, 12. 



/. Not inclined ; pear-shaped, or globular with spines 

 at the summit. Diffiugia, 6. 



f. Inclined; circular or oblong, thicker and with 



spines at the rear. Centropyxis, 7. 



g. Shell brown (A). 



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



g. Shell often yellowish, ovoid, curved (retort shaped), 

 mouth circular. Cyphoderia, 11. 



h. Circular, with or without marginal teeth. Ar- 

 cella, 8. 



i. Mouth smooth, circular; shell inclined, without 

 spines. Trinema, 9. 



i. Mouth serrated ; shell not inclined, formed of hex- 

 agonal plates ; often spinous. Euglypha, 10. 



1. AMCEBA (Fig. 92). 



There is hardly a living animal so soft and changea- 

 ble 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 at 

 the forward part of the moving creature. The front 

 may, with scarcely a warning, become the rear as the 



