Phylum I. PROTOZOA. 



Protozoa are unicellular organisms with bodies consisting of sarcode (proto- 

 plasm), usually very minute, frequently microscopic in size, and without 

 difFerentiated tissues or organs, They are water-inhabitants, take in nourish- 

 ing matter either at any point on the periphery of the body whatsoever, or 

 through a so-called moiith (cytostome), and reject the undigested portions either' 

 from any part of the body whatsoever, or from a definite point called the anal 

 aperture (cijiopijge). The contractile sarcode almost invariably contains one 

 or more nuclei, and exhibits considerable diversity of structure and difFerentia- 

 tion. Locomotion is accomplished by means of vibratile cilia, flagella, pseudo- 

 podia or irregulär processes of the periphery. Reproduction takes place by 

 means of budding or self-division, which latter process is often preceded by a 

 temporary conjugation of two individuals. Protozoa are divided into four 

 classes, only the first-named of which is known to occur in the fossil State : 

 Sarcodina, Flagellata, Infusoria and Gregarina. 



Olassl. SARCODINA. 



Protozoa with or without a test, having in fully developed individuals well 

 charaderised pseudopodia, either digitale, reticulate or radiale, with or without axial 

 filaments. 



Subclass 1. RHIZOPODA. 



Sarcodina either naked or with a definite test, the pseudopodia either lohose or 

 reticulate ; the adult form is amoeboid. 



Order 1. AMOEBIDA. 



The animals constituting this order do not occur as fossils. There are 

 found, however, in chalk and many marine limestones minute calcareous 

 bodies resembling coccoliths, such as are present in vast quantities in deep-sea 

 ooze of existing oceans.^ 



^ To the Amoebida were foniierly assigned by Huxley and Haeckel the so-called Bathybius, a 

 reticulated colloidal snbstance coniposed of anastomosing Strands, occuiring at great depths in the 

 Atlantic Ocean. Sir Wyville Thomson and Moebins regarded it as aprecipitate of calcium siilphate, 

 intermingled with decomposed organic matter. In deep-sea ooze, which consists chietly of linie 

 carbouate, as well as in Bathybius, great quantities of minute calcareous bodies of various shapes 

 are found, such as also occur as an essential constituent of chalk, marls and most marine lime- 

 stones belonging to older geological periods (cf. C. W. Gümbel, Neues Jahrbuch für Mineralogie, 

 1870, p. 7f>3). Ehrenberg termed these bodies morpholites, and regarded them as inorganic in 

 VOL. I 17 C 



