obtained from them far too costly to compete with silk-worm silk. [Illustration: FIG. 51.—The common garden spider, more correctly called the white cross spider (_Epeira diadema_): a female drawn a little (one-fifth) larger than life.] A number of different kinds of the lower animals besides spiders have the power of producing threads. The caterpillars of some moths are especially noted for this, since their thread is familiar to us all as “silk.” It is secreted as a viscid fluid by a pair of tubes opening at the mouth, and hardens on escape. Even some marine creatures—the mussels—produce threads, in this case from a gland or sac in the muscular foot, by means of which they fix themselves to rocks. A very big mussel—the _Pinna_—called _Capo lungo_ by the Mediterranean fishermen and _Capy longy_ at Plymouth, where they are also found, produces a sufficient quantity of fine horny threads to be used in weaving, and gloves have been made at Genoa from the shell-fish silk. The threads produced by the hardening of the tenacious fluid exuded by these various animals were probably simply protective in origin. The curious caterpillar-like creature _Peripatus_ spits out a viscid fluid when it is disturbed, which hardens into threads, and hopelessly entangles any small enemy which may venture to attack it. Threads of a poisonous nature are thrown out by jelly-fishes, polyps, and sea anemones, and serve them both as defence and as means of paralysing and capturing prey. A later stage in the use of such threads is their “felting” to form a case or tube (as in the sea anemone called _Cerianthus_), and so their application has gradually developed to the formation of egg-cases, snares, and the wonderful web of the geometric spider, and the countless “flying-lines” of smaller spiders, which make up the mysterious thing we call “gossamer.”