VI ANTENXATA— INTEGUMENT AND GLANDS 459 



and lai'VEe of Tcnthrcdinidm). The thread-like secretion of tliese glands, which 

 hardens when exposed to the air, forms the web of which the pupal envelope consists, 

 but it may also serve for other purposes. The serieteries are glandular tubes which 

 are paired, elongated, and coiled, often running through the whole length of the body ; 

 the glandular cells of their epithelium often attain to an enormous size, and have cell 

 nuclei in the form of branched networks. The 2 ducts unite, like those of the 

 salivary glands, to form an unpaired terminal duet, whose aperture also lies near the 

 mouth. Accessory glands may also open into the duets of the serieteries. The ducts 

 of these and other dermal glands have a chitinous iutima, which, like the tracheal 

 intima, may become thickened in a close spiral line. 



The spinning glands of Scolopcndrella have already been mentioned when describ- 

 ing the rudimentary abdominal limbs. The glands there mentioned as emerging 

 through pores at the points of stylets on the anal segment, and through the pleural 

 pores of the last leg-bearing segment, are also said to be spinning glands. 



Recalling t\\e[Protraclimta, we are led to suppose that the salivary glands of the 

 Antennata are transformed nephridia, and that the spinning glands belong to the 

 same category as the coxal glands of Perijxdus and the parajiodial setiparous glands 

 of the Cliaetopoda. Compare also on this subject the section on the rudiments of 

 abdominal limbs in the Hcxaimda. 



The morphological worth of the other numerous dermal glands which have been 

 observed in the Antennata cannot at present be rightly estimated. AVe can only 

 name a few of them. 



The Myriapoda {Diplo'j)oda) have stink glands for protection, which emerge 

 through the "foramina repugnatoria " on the dorsal side of a varying number of trunk 

 segments. These foramina are either paired, in which case they lie laterally, or 

 unpaired in the middle line. In Paradesmus gracilis the secretion of the protective 

 glands contains prussic acid. These protective glands, of which only 1 pair occurs 

 in a double segment, have been regarded as modified nephridia. 



The glands of the GeopMlidce among the CMlopoda, which emerge through 

 unpaired median ventral pores, may perhaps belong to the category of protective 

 glands. 



Stink glands, which yield a strongly smelling secretion evidently serving as a 

 protection to the animal, are also found in many Insects (especially Hctcroptera, 

 Coleoptera, and Ortlioptera). They are sometimes paired, sometimes luipaired, and 

 emerge at different points of the body. In many Coleoptera these organs are appen- 

 dages of the rectum. An enumeration of the recorded observations, however, could 

 at present yield nothing of special interest to the comparative anatomist. 



Poison glands. — The maxillipedes of the CMlopoda contain poison glands whose 

 outer aperture Ues in the terminal claws. In the female of many Hymenoptera a 

 poison gland occurs, which pours its secretion into a stinging apparatus of complicated 

 structure placed at the posterior end of the body. The poison gland itself consists 

 of 2 simple or branched glandular tubes, which enter a poison vesicle or reservoir by 

 means of a common unpau'ed terminal piece (c/. Fig. 347, A, p. 487). 



Leg glands are found in many Insects on the terminal joints of the thoracic legs. 



Wax glands occur in many Rliynchota {Apihides, Coccidce). They lie either on 

 the back in cross rows, or near the anus, and secrete filaments, plates, etc. , of wax ; 

 these are used either for forming a dorsal shield or a down which covers the body, or 

 for enveloping the excrement. 



Rectal glands are papillfe or thickenings with glandular epithelium, very 

 commonly found in the rectum of Insects. 



In Mantis glands enter the coxte of the 1st pair of legs (coxal glands ?). 



