. The biology of spiders. Spiders; Insects. 74 THE BIOLOGY OF SPIDERS The ampullaceal and cylindrical glands are composed of a layer of cellular secretory epithelium inside, covered with peritoneal membrane. The former alone is continued into the duct, a fact which distinguishes these glands from the aciniform and pyriform. This is shown in Fig. 48 which was drawn from a double-stained preparation, made by L. W. Spratt, one of my pupils at Malvern. The function of the aggregate or tree-shaped glands is problematical. They are found only in the three highest families, the Linyphiidae, the Theri
. The biology of spiders. Spiders; Insects. 74 THE BIOLOGY OF SPIDERS The ampullaceal and cylindrical glands are composed of a layer of cellular secretory epithelium inside, covered with peritoneal membrane. The former alone is continued into the duct, a fact which distinguishes these glands from the aciniform and pyriform. This is shown in Fig. 48 which was drawn from a double-stained preparation, made by L. W. Spratt, one of my pupils at Malvern. The function of the aggregate or tree-shaped glands is problematical. They are found only in the three highest families, the Linyphiidae, the Theridiidae, and the Epeiridae, whose species possess six of these glands, two smaller than the other four. They lie near and usually above the cylin- drical glands and are irregu- larly-shaped branching masses, characterised by projecting caeca on their surfaces. The proximal part of the duct is also similarly studded with knots of cells. The three glands on each side open to- gether on the inner side of each inferior spinneret. While the function of these glands is un- certain, it is generally believed that they supply the very Fig. Cylindrical Gland. dastic gilk of the spiml thread in the orb-web and the viscid drops which coat it. Such threads do occur, though rarely, as components of the webs made by members of the other two families which possess aggregate glands. The lobed glands are peculiar to one family, the Theri- diidae. In the chapter on external structure, this family was mentioned as possessors of a comb of stiff hairs on the tarsal joints of the fourth pair of legs. The combs are used. 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 Savory, Theodore Horace, 1896-. London : Sidgwick & Jackson
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecti, booksubjectspiders
