. Cassell's natural history. Animals; Animal behavior. TES TUBE-MAKERS. feet, with two hooked set* and cirri or pimples. There are no blood-vessels. These curious live on the surface of Comatulae, kinds of Echinoderms. Their larvaj are ciliated all over, and the head and feet develop gradually. Probably the position of the worm is amongst the Polychicta. SUB-OEDER —THE TUBE- MAKERS. These worms live in more or less solid tubes, which they construct of diflerent sub- stances such as mud and excreted mucus mixed with calcareous matter, gi-ains of sand and pieces of shells. Some live in
. Cassell's natural history. Animals; Animal behavior. TES TUBE-MAKERS. feet, with two hooked set* and cirri or pimples. There are no blood-vessels. These curious live on the surface of Comatulae, kinds of Echinoderms. Their larvaj are ciliated all over, and the head and feet develop gradually. Probably the position of the worm is amongst the Polychicta. SUB-OEDER —THE TUBE- MAKERS. These worms live in more or less solid tubes, which they construct of diflerent sub- stances such as mud and excreted mucus mixed with calcareous matter, gi-ains of sand and pieces of shells. Some live in mud, or in penetrations in rocks, and others drag their tubes after them. The Tubicolje have a not very distmct head, a short, often not jirojectable proboscis, and no jaws. The branchijB ai-e either deficient, or are limited to two or three segments behind the head. The exception is in the Lob Worm, where they are placed on the back of the median segments. There are numerous filiform tentacles and ten tacular cirri on the head, and one or moi'e opercula on it. The feet are short; their ac- cessory structures ai-e small, and are of no use in swimming; but the lobes of the feet have capillary setse, and the inferior are pro- jections \v\i\\ hooked setse or flat hooks. The eyes may or may not be present, and are found in many situations, as are also the branchial tufts, when they are very numei-ous. The body may be divided into two or thiee regions, the seg- ments of each differing in their shape and in the kinds of appendages. They are not carnivorous, and are said to feed upon vegetable matter. The long tentacles are of use in building the tubes. The development of these worms may be in some instances retrogressive; organs degrad- ing and degenerating for want of use. In one gi-oup (Spirorbis) the eggs and larvae are earned about by the mother in a pouch, and when they are able to comtruct a tube for themselves they escape. The larvje are mostly free and ciliated, an
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Keywords: ., bookcentury1800, bookdecade1890, booksubjecta, booksubjectanimals
