The Protozoa / by Gary N. Calkins.

Date:
1901
Catalogue details

Licence: In copyright

Credit: The Protozoa / by Gary N. Calkins. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    other flagellated forms, perhaps from forms like the Vampyrelliclae. On the whole, there is no conclusive evidence to support the view that Rhizopoda are more primitive than Flagellidia, or vice versa. Their mutual affinities are very close, and together they stand as the most primitive forms of modern Protozoa. The relations of the Radiolaria to the Ileliozoa are extremely close, and there is abundant evidence to show that the former were derived from the latter by the acquisition of a chitinous membrane between ectoplasm and endoplasm, and the retention of a gelatinous mantle like that of Spheemstrum (Haeckel). As first pointed out by Brandt (’85), tbe young Radiolaria pass through flagellated and amoeboid swarm stages, then through Heliozoa stages, until the definitive radiolarian structure is attained. Haeckel described the intermediate forms which are represented in this growth, as flagellate, amoeboid, Actinoplirys, Spheemstrum, and Aetissa, the last being the simj^lest of the Radiolaria. Although the external appearance of a radiolarian is strikingly similar to that of a heliozoon, there is no structure in Heliozoa to compare with the chitinous central capsule of the Radio- laria. Greeff (’67, ’71) described a membrane-like thickening between the endoplasm and the ectoplasm of Aetinosphecrium, and regarded it as homologous with the central capsule. Other observers, c.g. F. F. Schultze, Hertwig and Lesser, Biitschli, etc., have not seen it, and the latter, especially, considers Greeffs contribution of little value. However incorrect his interpretation may have been that Aetinosphee- riuin is a fresh-water radiolarian belonging to the Acantharia, Greeff was not mistaken in his observation, for an occasional specimen is found which shows such a membrane (Fig. 58). CLASSIFICATION Class I. SARCODINA. Naked or shelled Protozoa, characterized by the possession during adult life of movable or changeable processes of protoplasm, the pseudo- podia, which may be finger-form, reticulate, or ray-like, and which may or may not have axial filaments. Reproduction is brought about by simple division and by spore-formation. Subcla.ss I. RHIZOPODA. Naked or shelled Sarcodina having pseudopodia of the lobose (finger-formed) or reticulate (anastomosing) type. The adult form is amoeboid : the young forms- are amoeboid or flagellated, and are produced by spontaneous division of the cell during active phases or during encystment. The adults in some cases fuse to form plasmodia. Order I. AMCEBIDA. Rhizopoda provided with lobose pseudopodia, with or with- out a shell, with one or more nuclei, and usually with a contractile vacuole. Suborder i. GYMNAMCEBINA. Naked forms of Amoebida having lobose pseudo- podia, and with or without nucleus and contractile vacuoles. Family i. AMCEBID.®. The pseudopodia are lobose. occasionally sharp pointed and branched. Genera: y/wa'/w, marine and fresh water; Parannrba Schau- dinn ('96); Protamoeba Haeckel ('66). marine and fresh water: Gringa