24 



PROTOZOA. 



frequently an accessory opening on each side of the main axis of the opposite 

 pole ; sometimes several central capsules in one individual ; always with extra- 

 capsular pigment mass (Phceodium H.), which covers the region of the main 

 opening. Skeleton either purely silicious, or weakly silicated with much 

 organic suhstance, always extracapsular, rarely absent. 



Fam. 17. Phaeocystina. Partly without skeleton, partly with loose skeletal 

 structures ; central capsule in the centre of the spherical body. Phceodinia H. 

 Aulacantha H., Auladinium H. 



Fam. 18. Phaeosphaeria. Fam. 19. Phaeogromia. Fam. 20. Phaeoconchia. 



\ If: 



Fict. 19.Eucyrtidium cranoidcs (after E. Haeckel). 



Class II. INFUSORIA.* 



Protozoa with a definite form, provided with an external membrane, 

 and bearing either flagella or cilia. Mouth and anus usually, 

 contractile vacuole and one or more nuclei always present. 



* Ehrenberg, Die Infusionsthierchen als vollkommene Organismen, 1838. 

 Balbiani, "Etudes sur la Reproduction des Protozoaires. " Journ. de la Phys., 

 Tom. III. Balbiani, "Recherches sur les phenomenes sexuels^les Infusoires." 

 Journ. de la Phys. , Tom. IV. Claparede und Lachmann, Etudes sur les Infu- 

 soires et Us Rhizopodes, 2 vol. Geneve, 1858-1861. E. Haeckel, "Zur Morphologic 



