The spermatozoa differ from those of other animals in having the form of cells which sometimes perform amoeboid movements.
In individuals either of the male or female sex, germ-cells which are quite undifferentiated and neutral in character, become amoeboid, and wander into the endoderm.
In Hydra the odcyte is a large amoeboid cell, which sends out pseudopodia amongst the odgonia and absorbs nutriment from them.
These are amoeboid cells and are extremely phagocytic, their power of digestion being greatly developed.
The first observation of a trypanosome is usually ascribed to Valentin (55), who in 1841 announced his discovery of certain amoeboid parasites in the blood of a trout.
Ingestion and dissolution of the Trypanosomes by phagocytes has frequently been observed; and it is probable also that the haematopoietic organs secrete some substance which exerts a harmful action on the parasites, and causes them to undergo involution and assume weird-looking " amoeboid " and " plasmodial " forms.
It was formerly the custom to include with the Fungi the Schizomycetes or Bacteria, and the Myxomycetes or Mycetozoa; but the peculiar mode of growth and division, the cilia, spores and other peculiarities of the former, and the emission of naked amoeboid masses of protoplasm, which creep and fuse to streaming plasmodia, with special modes of nutrition and spore-formation of the latter, have led to their separation as groups of organisms independent of the true Fungi.
Monoblepharis has oogonia with single oospheres and antheridia developing a few amoeboid uniciliate antherozoids; these creep to the opening of the oogonium and then swim in.
On the other hand, the uniciliate zoospores of Polyphagus have slightly amoeboid movements, and in this and the pseudopodium-like nature of the protoplasmic processes, such forms suggest resemblances to the Myxomycetes.