122 THE SMALLEST LIVING THINGS 



Leucosin : a chemical substance of unknown origin composing certain glistening 



bodies in the cells of some of the plant-flagellates. 

 Macrogamete (or Megagamete) : the larger, or female, of two gametes. 

 Macronucleus (plural, macronuclei) ; the larger of the two kinds of nuclei of 



infusoria. 

 Matrix (from the Latin, mater, meaning "mother") : substance from which 



structures are formed, or in which they are embedded. 

 Maturation : the final series of stages in the formation of the egg or the sperm by 



which its nucleus is prepared for union. 

 Meiosis (adjective, meiotic), the process of being made smaller; technically the 



processes of nuclear division in maturation (q.v.) of the germ cell. 

 Metabolism : the chemical changes proceeding continually in living cells, by which 



the energy is provided (destructive metabolism) for the vital processes and 



activities (see page 88), and new material is prepared and assimilated to 



repair the waste (constructive metabolism). 

 Metaphyte (plural, metaphytes) : a multicellular plant. 



Metaplastid : a product of cell activity which remains stored up in the protoplasm. 

 Metazoa (singular, metazoan) ; multicellular animals. 

 Microgamete: the smaller, or male, of two gametes. 

 Micronucleus (plural, micronuclei) ; the smaller of the two kinds of nuclei 



of infusoria. 

 Mixotrophic : deriving nourishment from a combination of any two or even all 



(three) of the following methods of food-getting: holophytic, holozoic, and 



saprozoic. 

 Monad (from the Greek word meaning "alone" or "unit"): a minute, simple 



flagellated organism. 

 Morphology (adjective, morphological) ; the branch of biology dealing with the 



form and structure of animals and plants ; the study of the forms, relations, 



changes, phylogenetic (see Phylogeny, below) development of organs apart 



from their functions. 

 Motile : exhibiting, or capable of, spontaneous movement. 

 Motile phase : the stage of the life history of an organism during which it is 



free swimming. 

 Mutation : a sudden heritable change in some aspect of the organism, due to an 



alteration in the hereditary material. 

 Myonemes : thread-like muscular elements found in gregarines and in ciliated 



protozoa. 

 Nucleoproteins : any of a class of compound proteins (q.v.) found in nearly all 



cell nuclei, in protoplasm, etc. 

 Nucleus (plural, nuclei; from the Latin meaning "little nut" or "seed"): the 



central body, with specialized structures and functions, found in nearly all cells. 

 Nutrition : the aggregate of activities having to do with obtaining food, digesting 



and assimilating it, and adding it to the protoplasmic substances already present. 

 Obligatory: in biology, the state of being limited to a single life condition, e.g., 



parasites ; opposed to "facultative," which means having the power to live 



under different conditions. 

 Osmosis : the passing of a fluid through a porous partition, such as a membrane, 



to mix with another fluid on the other side. The inward flow is called 



Endcsmosis, and the outward flow Exosmosis. 

 Optimum (from the Latin, meaning "best") ; the most favorable condition as to 



temperature, light, moisture, food, etc., for the growth and reproduction of 



an organism. 

 Oxidation : the process of combining with oxygen, or with more oxygen. 

 Palmella phase : a quiescent phase in the life history of a plant flagellate during 



which the organism is embedded in a gelatinous substance. 

 Paramylum : a carbohydrate (C0H10O5), allied to starch, found in unicellular 



organisms. 

 Parthenogonidium (plural, parthenogonidia) : (1) an individual which can 



be produced by a colony by one of the asexual methods — cell-division, spore- 

 formation, budding, etc., but does not include the self-fertilization of hermaph- 

 roditic organisms; (2) an asexually produced individual. 

 Pathogenic (from the Greek word pathos, meaning "suffering," and the suffix 



genie, meaning "generating" or "producing") : causing disease. 



