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 substance, always extracapsular, rarely absent. 



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

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

 Aulacantha H., Aulactinium H. 



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



FIG. 19.Eucyrtidiim cwwioitfes (after E. Haeckel). 



Class II. INFUSORIA.* 



Protozoa with a definite form, provided icith an external memlrane, 

 and learinij either fiagella or cilia. Mouth and anus usually, 

 contractile vacuole and one or more nuclei always present. 



* Ehrenberg, Die Infusionsthicrchen als vollkommene Organismen, 1838. 

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

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

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

 soires et les Jihizopodcs, 2 vol. Geneve, 1858-1861. E. Haeckel, "Zur Morphologic 



