. A text-book of invertebrate morphology. Invertebrates. TYPE ARAGHNIDA. 467 developed system of muscle-bands. There are no special organs either for respiration or circulation. The mouth, surrounded by papillae (Fig. 214, p), lies at the anterior extremity of the body, and leads into a tubular mouth-cavity containing, imbedded in its walls, a pair of chitinous or partly calcareous teeth, and receiving the ducts of two glands {sg) which have been regarded as salivary or perhaps poisonous in function. Behind, this cavity opens into a muscular pharynx (pA) which is connected by a short oesophagu
. A text-book of invertebrate morphology. Invertebrates. TYPE ARAGHNIDA. 467 developed system of muscle-bands. There are no special organs either for respiration or circulation. The mouth, surrounded by papillae (Fig. 214, p), lies at the anterior extremity of the body, and leads into a tubular mouth-cavity containing, imbedded in its walls, a pair of chitinous or partly calcareous teeth, and receiving the ducts of two glands {sg) which have been regarded as salivary or perhaps poisonous in function. Behind, this cavity opens into a muscular pharynx (pA) which is connected by a short oesophagus with the mid-gut. At the Junction of this with the rectum or hind-gut is a pair of csecal diverticula (Ig), probably Malpighian tubules, and into the hind-gut there also open the ducts of the reproductive organs, the hind-gut thus serving as a cloaca. It opens on the ventral surface of the body a short distance from the pos- terior extremity and therefore in front of the last pair of appendages. The nervous system consists of a supraoesophageal ganglion (ce) united with a chain of four pairs of ventral ganglia. No special sense-organs occur except two eyes situated at the sides of the head. The sexes are distinct, the reproductive organ being unpaired and opening into the cloaca, into which opens also in both sexes an unpaired accessory gland. The Tardigrada occur in water usually, especially in such locations as the gutters on the roofs of houses, though some- times found also among moss. The group contains but a small number of genera, of which Macrobiotus is perhaps the most Fig. 214.—Diagram of Structure of Macro- biotus Hufelandii (com- bination of figures by Plate). an = anus. ce = cerebral ganglion. dg = dorsal gland. Ig = lateral gland or Mal- pighian tubule. m = muscle. ov = ovary. p = papillae. ph = pharynx. sg = salivary(?) Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
