. Elementary text-book of zoology. Zoology. HTDROZOA SIPHONOPHOBA. 245 possess a circle of tentacles. They always, however, have a long tentacle arising from their base. This tentacle can be extended to a considerable length, and be retracted into a spiral coil. It rarely has a simple form, but, as a rule, it bears a number of unbranched lateral twigs, which are also very contrac- tile. These tentacles are invariably beset with a great number of nema- tocysts, which in many places are closely packed and have a regular arrangement. These aggregations of thread-cells are especially found on the
. Elementary text-book of zoology. Zoology. HTDROZOA SIPHONOPHOBA. 245 possess a circle of tentacles. They always, however, have a long tentacle arising from their base. This tentacle can be extended to a considerable length, and be retracted into a spiral coil. It rarely has a simple form, but, as a rule, it bears a number of unbranched lateral twigs, which are also very contrac- tile. These tentacles are invariably beset with a great number of nema- tocysts, which in many places are closely packed and have a regular arrangement. These aggregations of thread-cells are especially found on the lateral branches of the tentacles, and give rise to large, brightly-coloured swellings, the batteries of nematocysts. The batteries show considerable variations a I. FIG. 187.—Group of buds of a Physophor at the bottom of the pneumatophore. C, Central cavity ; S/c, nectocalyx bud with the ectodermal Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G. (Frederick Granville), b. 1858. New York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
