. Text-book of zoology for schools and colleges. Zoology. 38 INVERTEBRATE ANIMALS. a distinct formation. It attains in places a thickness of several thousand feet, and is espeoiaUy largely developed in the Alps. It has an historic in- terest from the fact that the Pyramids are built of it, and that the Nummu- Utes in it were noticed by Herodotus, the " father of ;. Fig. 5.—NummvlUes l(xmgatu9. Obdee IV. Rabiolahia (Lat. radius, a ray).—The third order of the Rhizopoda is that of the Madiolaria, essentially distinguished hy the fact that the saroode-body has the power of secre
. Text-book of zoology for schools and colleges. Zoology. 38 INVERTEBRATE ANIMALS. a distinct formation. It attains in places a thickness of several thousand feet, and is espeoiaUy largely developed in the Alps. It has an historic in- terest from the fact that the Pyramids are built of it, and that the Nummu- Utes in it were noticed by Herodotus, the " father of ;. Fig. 5.—NummvlUes l(xmgatu9. Obdee IV. Rabiolahia (Lat. radius, a ray).—The third order of the Rhizopoda is that of the Madiolaria, essentially distinguished hy the fact that the saroode-body has the power of secreting a " siliceous " or flinty skeleton, either in the form of a shell, or of detached spicules or needles; while the pseu- dopodia are long and thread-like, and stand out from the body like rays. In this last character the Madiolaria approach very closely to the Foraminifera; and the resemblance be- tween the two groups is still further increased by the fact that the pseudopodia often run into one another so as to form a net-work, and sometimes show a circulation of granules along their edges. Three groups of organisms have been described as belonging to the Madiolaria, and we may briefly notice an example of each of these. In the first family we have organisms like Acanthometra (Fig. 6, a), in which the body is composed of sarcode, sup- ported by a framework of siliceous or flinty rods, which eJI meet in a common centre. The spines or rods are all perfo- rated by canals, and each conveys a pseudopodium, which is protruded from an aperture at its apex. Many pseudopodia, however, are given off from the surface of the body directly, and are not enclosed in the spines. The AcanthometroB are all minute, and are found floating near the surface in the open ocean, sometimes in great numbers. In the second family {Polycystina, Fig. 6, b) we have a number of beautiful little organisms closely allied to the Fo- raminifera, but differing in the fact that the body is enclose
Size: 2608px × 958px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
