. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE ANNELIDA. 206 im jh )e le re. FlG, \ c 98.—Pauapodium of Nereis virena. br = bi'Hiicliia. de = dorsal cirrus. 8 — setae. ve = ventral cirrus. cations of the cirri or brauclies arising from tliem, and respiratory in function, also occur. Muscles pass from the body-wall to the parapodia, which thus ^..^..^s-dc become important organs of locomo- tion and in some of the actively swim- ming species assume a more or less flattened plate-like form. The head segment is gen
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). TYPE ANNELIDA. 206 im jh )e le re. FlG, \ c 98.—Pauapodium of Nereis virena. br = bi'Hiicliia. de = dorsal cirrus. 8 — setae. ve = ventral cirrus. cations of the cirri or brauclies arising from tliem, and respiratory in function, also occur. Muscles pass from the body-wall to the parapodia, which thus ^..^..^s-dc become important organs of locomo- tion and in some of the actively swim- ming species assume a more or less flattened plate-like form. The head segment is generally well diflferentiated from those which succeed it, being destitute of parapodia and setse, and as a rule carrying a number of appendages sensory in function, and being likewise usually provided with eyes. The cephalic appendages may be short and rather stout, forming what are termed palpi (Fig. 100, p), or somewhat longer and more slender, forming the drri (c), or even still more slender, being then known as tentacles (t). The body is enclosed in a chitinous covering secreted by the subjacent ectoderm, here known as the hypodermis (Fig. 99, hy). The musculature of the body-wall which lies below the hypodermis is separated from this by a basement-mem- brane and consists of an external layer of circular fibres {cm) and a subjacent layer of longitudinal fibres {Im) which is, as a rule, interrupted in the mid-dorsal and ventral lines and also in the region of the two lobes of the parapodia so as to form four bundles. Special muscles extend from t)ie body- wall to the base of the seta-sacs, and furthermore a pair of muscle-bauds cross the cavity of each metamere, in typical cases passing from the lateral regions of the dorsal surface downwards and inwards to be inserted into the ventral body- wall on each side of the median line. The inner surface of the longitudinal muscle-layers is lined with a layer of peri- toneal cells which completely enclose the coelom (co) of eac
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
