. A manual of zoology. Zoology. GENERAL ANATOMY 53 urchin; that a species of amoeba always performs only the movements characteristic of tha,t species, we must assume that the functioning part of this cell, the protoplasm, has in each case its peculiarities. We are driven to the assumption of an almost unlimited diversity of protoplasm, even if we concede an important share in the prominent differences to the nucleus, of which we shall speak later. General Properties of Protoplasm.—The similarity of protoplasm expresses itself in its appearance and in its vital phenomena. Under slight magnific
. A manual of zoology. Zoology. GENERAL ANATOMY 53 urchin; that a species of amoeba always performs only the movements characteristic of tha,t species, we must assume that the functioning part of this cell, the protoplasm, has in each case its peculiarities. We are driven to the assumption of an almost unlimited diversity of protoplasm, even if we concede an important share in the prominent differences to the nucleus, of which we shall speak later. General Properties of Protoplasm.—The similarity of protoplasm expresses itself in its appearance and in its vital phenomena. Under slight magnification, protoplasm appears as a faintly gray substance (sometimes colored yellowish, reddish, etc., by pigments) in which numerous strongly- refracting granules are imbedded. The vital characteristics of this sub- stance are movement, irritahility, power of assimilation and of reproduction. By using higher powers a finer structure can be seen in the 'homogeneous protoplasm' of earher writers. It looks like a iine-meshed framework {filar substance, spongioplasm, cell retictilwn) the interstices of which are filled with other material (interfilar substance, enchylcma, ground substance). The question whether this framework is formed of threads and trabeculae or whether the appearance is not formed by small cham- bers, bounded by fine partition-walls (foam structure of protoplasm), such as results when two fluids which do not mix (like olive oil and soda solution) are shaken together until a very fine froth is produced. This view that protoplasm has a foam structure how it can be a fluid aggregate with a fine structure. Regarding the fluid aggregate condition cf protoplasm (long called a 'solid-fluid') there has been much dispute. Exact re- searches regarding its physical condition show that it behaves hke a fluid. Movement of Protoplasm.—Move- ment expresses itself first in changes of form of the whole body—amoeboid move- ment—and secondly in the change of positio
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