212 EVENINGS AT THE MICROSCOPE. 



and other caterpillars ; but the apparatus by which it is 

 secreted, and that by which it is spun, are both far more 

 complex and elaborate than those of the latter. Generally 

 speaking, there are three pairs of spinnerets, or external 

 organs, through which the threads are produced ; but in 

 some few cases there are only two pairs,* and in others, 

 as the Garden Spiders (Epdra), the hindmost pair seem 

 to be united into a single spinneret. These are always 

 situated at the hinder extremity of the body, and I will 

 show them to you presently. First, however, I will de- 

 scribe the internal apparatus ; the source of the threads. 



The glands which secrete the gummy fluid are placed in 

 the midst of the abdominal viscera, and in some instances 

 ■ — as in the female of Epdra fasdata, a species which 

 makes a remarkably large web — they occupy about a 

 quarter of the whole bulk of the abdomen. About five 

 different kinds of these glands may be distinguished, 

 though they are not all present in every species. The 

 Epdra, however, present them all. 



In this genus there are : — 1. Small, pear-shaped bags, 

 associated in groups of hundreds, and leading off by 

 short tubes, which are interlaced in a screw-like manner, 

 and open in all of the spinnerets. 2. Six long twisted 

 tubes, which gradually enlarge into as many pouches, and 

 then are each protracted into a very long duct, which 

 forms a double loop. 3. Three pairs of glandular tubes, 

 similar to the preceding, but which open externally through 

 short ducts. 4. Two groups of much-branched sacs, whose 

 long ducts run to the upper pair of spinnerets. 5. Two 

 slightly-branched blind -tubes, which terminate by two 

 short ducts in the middle pair of spinnerets. | 



It is not very easy to examine the spinnerets with a 



* " There is a fourth pair in Mr. Blackwall's family of the Cini- 

 Jloridce, situate in front of the ordinary anterior pair." (Meade.) 



f See a valuable account, by Mr. R. H. Meade, of the secreting glands 

 in Spiders, and of the distinct functions of the various kinds of these 

 organs, read at the British Association, Sept. 25th, 1858. 



