Phylum I. PROTOZOA. 



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

 }Dlasm), 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 mouth (ci/fosiome), and reject the undigested portions either 

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

 aperture {cijtopyge). 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 irregular 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. 



Class 1. SARCODINA. 



Frotozoa with or without a test, liaving in fully developed individuals tvell 

 characterised pseudopodia, either digitate, reticulate or radiate, with or without axial 

 filaments. 



Subclass 1. RHIZOPODA. 



Sarcodina either naked or ivith 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 formerly assigned bj' Huxley and Haeckel the so-called Bathyhius, a 

 reticulated colloidal substance composed of anastomosing strands, occurring at great depths in the 

 Atlantic Ocean. Sir Wyville Thomson and Moebius regarded it as a precipitate of calcium sulphate, 

 intermingled with decomposed organic matter. In deep-sea ooze, which consists chiefly of lime 

 carbonate, as well as in Bathyhiiis, great quantities of minute calcareous Ijodies 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. G'ainhel, Neues Jahrbuch fiir Mineralogie, 

 1870, p. 753). Ehrenberg termed these bodies morpholites, and regarded tlieni as inorganic in 



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