. The Cambridge natural history. Zoology. RHIZOPODA- 55 nous. Again, the shell may be encrusted with sand-grains derived directly from without, or from ingested particles, as shown in Centropyxis, Bifflugia (Fig. 10, D), Heleopera, and Campascus when supplied with powdered glass instead of sand. The cement in Bifflugia is a sort of organic mortar, infiltrated with ferric oxide (more probably ferric hydrate). In Lecquen- reusia spiralis (formerly united with Bifflugia) the test is formed of minute sausage-shaped granules, in which may be identified the partly dis- solved valves of Diatoms taken
. The Cambridge natural history. Zoology. RHIZOPODA- 55 nous. Again, the shell may be encrusted with sand-grains derived directly from without, or from ingested particles, as shown in Centropyxis, Bifflugia (Fig. 10, D), Heleopera, and Campascus when supplied with powdered glass instead of sand. The cement in Bifflugia is a sort of organic mortar, infiltrated with ferric oxide (more probably ferric hydrate). In Lecquen- reusia spiralis (formerly united with Bifflugia) the test is formed of minute sausage-shaped granules, in which may be identified the partly dis- solved valves of Diatoms taken as food ; it is spir- ally twisted at the apex, as if it had enlarged after its first formation, a very rare occurrence in this group. The most frequent mode of fission in the tes- taceous Ehizopods (Figs. 8,10) is what Schaudinn aptly terms "bud-fission," where half the protoplasm protrudes and accumu- lates at the mouth of the shell, and remains till a test has -formed for it, while the other half re- tains the test of the original animal. The materials for the shell,. Fig. 10.—Test-bearing Rhizopods. A, Quad-mla symmetrica ; B, Hyalospkenia lata ; C, Arcella vulgaris ; D, Dijfflvgiapyriformis. (From Lang's Comparative Anatomy.) whether sand-granules or plates, pass from the depths of the original shell outwards into the naked cell, and through its cyto- plasm to the surface, where they become connected by cementing matter into a continuous test. The nucleus now divides into two, one of which passes into the external animal; after this the two daughter-cells separate, the one with the old shell, the other, larger, with the new one. If two individuals of the shelled species undergo bud-fission in close proximity, the offspring may partially coalesce, so that a monstrous shell is produced having two Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of thes
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