ORGANS OF LOCOMOTION 531 



function of the protoplasm as such are found; also food particles, 

 pigment granules, oil drops, waste material and foreign material, like 

 lime or silica, more or less accidentally taken up into the body of the 

 organism. The granules, which contain stored food material, are 

 often called plastids, and plastids containing pigment are known as 

 chromatophores. 1 



Nucleus and Nuclear Substances. Protozoa generally contain two 

 nuclei. In some protozoa these cannot be well recognized as two 

 distinct nuclei, because they are, during the period of rest, contained 

 in one common nuclear membrane; in other protozoan organisms 

 they can always be well distinguished. Since one of the nuclei is 

 generally large and the other small, they have been called the macro- 

 nucleus and the micronucleus; the latter is also called the blepliaroblast, 

 because a flagellum may originate from it. The large nucleus is 

 generally concerned in the nutrition of the organism; hence it is 

 called the trophonucleus. The small or micronucleus is clearly 

 concerned in the reproduction and multiplication of the protozoan 

 organism, and, for this reason, Calkins recommends that it be called 

 the karyogonad, or the gonad nucleus, as representing the germ plasm 

 from which reproduction starts. This gonad nucleus, when contained 

 in a common nuclear membrane with the trophonucleus separates 

 from it during the period of maturation which precedes reproduction. 

 That portion of the nucleus which stains with the so-called nuclear 

 stains (hematoxylin, carmin, the basic anilin stains) is called the 

 chromatin. The latter under certain conditions may leave the nucleus 

 and become distributed diffusely in the form of granules in the 

 cytoplasm. Besides the chromatin the nuclei of protozoa contain 

 another very important substance, which apparently is the source of 

 energy of motion and metabolism; this substance has been called 

 kinoplasm (also archoplasm). Calkins calls this kinoplasm, whether 

 found inside or outside the nucleus, the division centre. Its importance 

 in relation to the function of locomotion is well recognized in trypano- 

 somes where the material of the undulating membrane, the flagellum 

 and the other contractile locomotory structures, is all derived from 

 this division centre, or kine to nucleus. 



Organs of Locomotion. 1. Pseudopodia. The most primitive form 

 of locomotion among protozoa is the ameboid motion, depending 

 upon the possession of pseudopodia (false feet). These are simply 

 digit-like prolongations or out-flowings of the cytoplasm. In ameba 

 the latter under favorable conditions is constantly in a flowing motion 

 combined with a constant change of shape. This ameboid motion 

 by the flowing and drawing action of the contractile protoplasm is 

 not only shown by certain protozoa, but also by some of the cells of 

 higher multicellular (metazoic) animals. The most important cells 



1 The term chromatophore in histology and histopathology of higher animals designates 

 pigment containing cells and not mere plastids. 



