F. M. CAMPBELL — OBSERVATIOXS ON SPIDERS. 39 



backwards to the abdominal intestine. Behind the suckinpj-stoniaoh 

 tlie intestine sends forward two branches, from each of whicli run 

 downwards four others (coeca). These vary in different species. 



On each side of, and attached to, the two lips, is a maxilla, which, 

 however, is but the basal joint of a six-jointed palpus. Part of the 

 external edges of the maxillne is strongly dentated. The maxilloe 

 have a lateral motion, and their function is to press the prey, thus 

 causing its juices to exude, while they also bring the parts so 

 treated within reach of the lips. 



The external spinning organs, or spinnerets, are situated at the 

 extremity of the abdomen. They consist of two, four, six, seven, 

 or eight jointed protuberances,* on which are numerous horny tubes 

 in communication with glands. These secrete a viscid fluid, which, 

 "when exposed to the atmosphere, quickly dries. Mr. Meade, in a 

 paper read before the British Association,! describes these glands 

 in detail, and holds that spiders may have the power of throwing 

 out threads without the assistance of any external force. From 

 a variety of experiments I am inclined to think that this is not 

 the case. 



The simplest method employed by a spider to draw out its 

 thread is to fasten it to some fixed object and then to move away. 

 If one be led to do this on a piece of glass, and the attachment be 

 microscopically examined from the inverted side, it will be found 

 to consist of many shreds, which at a little distance become united.;}: 

 As the spinnerets are jointed, a spider is enabled to direct them in 

 such a manner as to enable the liquid passing from each to dry at 

 different points, so that it can spin more than one thread at the 

 same time. The horny tubes vary in size, form, and arrangement 

 in different species, and their number with age. 



LiFE-HlSTOET. 



Spiders are oviparous, and there is no metamoi-phosis. They cast 

 their skins from time to time as they grow, and each whole 

 exuvium carries with it that of the two plates (which have already 

 been mentioned as being attached to the lips), the oesophagus, with 

 sucking-stomach, the spinnerets with tubes, and the pulmonary sacs 

 with laminoe. Blackwall obsei^ved nine moults in a Tegenaria eivi'lis; 

 and a T. domestica (house spider) which I had in confinement went 

 through this process on the following dates this year, 15th May, 

 9th June, 1st August, 21st Septembei'. On each occasion it was 

 completely exhausted after leaving the exuvium, and remained for 

 about twenty-five minutes hanging motionless, although it was 

 touched. Eggs are only laid by spiders when full grown, and the 

 age to which they live varies in different species, some dying the 

 autumn after they are hatched, and others not for several years. 



* British spiders have not less than six, in front of which in some families is 

 the seventh, in the form of a narrow band. This in some species is divided by a 

 line, thus making the eighth. 



t ' Report of the Twenty-eighth Meeting,' 1858, p. 157. 



X I refer to another plan under the heading of " Habits." 



