HANDBOOK OF 



Animal Classification, 



Class I.— PROTOZOA (First Animals). 



Characters. — The lowest class of animals grouped togetlier under the 

 class-name of PROTOZOA agree in the following characters; — (1) Through- 

 out life each animal remains a single cell ; (2) they are all very minute, and 

 mostly microscopic ; (3) they never reproduce by sexual meana. 



STJB-DIVISIONS. 



I. MONERA. — Amoeha-like Protozoa without a nucleus — e.g., Pro-- 

 tamoeba. 



II. ENDOPLASTICA. — Protozoa with one or more nuclei, subdivided 

 into three groups; — :(1) Ehizopoda — e.g. Amoeba; (2) Infusoria — e.g. Para- 

 moecium, Vorticella; (3) Gregarinidae — e.g. Gregarina. 



The remaining nine classes of animals are included under the term 

 METAZOA (after animals). The Metazoa all start life as a single cell 

 {ovum), which, by a series of changes, becomes developed into a mass of 

 numberless cells arranged in two or in three different layers (epiblast, 

 ectoderm, or outer layer; mesoblast, mesoderm, or middle layer; and 

 hypoblast, endoderm, or inner layer). 



