EVERSIBLE COXAL GLANDS 



369 



and in seizing a Thelyphonus with the forceps we have observed it to send out 

 from each side of the body a jet of offensive spray. 



We not infrequently find in myriopods (Polydesmidse, Julidse, and Glomeris) 

 repugnatorial or the so-called cyanogenic glands, which are either paired, open- 

 ing on the sides of the body, or form a single row along the median line of the 

 under side of the body. Leidy describes and figures the spherical glands of 

 Julus marginatus, of which there are 50 pairs. These glands have been regarded 

 as modified nephridia, but are more probably coxal glands, and the homologues 

 of the parapodial glands of annelid worms. 



Eversible coxal glands. True coxal glands occur in Scolopendrella 

 immaculata on the 2d to llth segment, on the inner side of the base 

 of the legs (Fig. 15, e.g.). Homologous glands also occur in the same 

 position in Campodea staphylinus (also in C. cookei and C. mexicana) 

 on the 1st to 8th abdominal 

 segments, and Oudemans has 

 described a pair of eversible 

 sacs on each side of seg- 

 ments one to seven of Ma- 

 chilis. These eversible sacs 

 in the synapterous insects 

 are evidently modified coxal 

 glands, and are probably re- 



rmcm a trivial a wpll a rprvir FIG. 358. Sternite of Macliilis maritima, with 



the pair of coxal sacs (el) on the right side everted ; 



atOl'V ill function ** coxa l appendages; m, retractor muscles. After 



Oudemans, from Lang. 



The apparatus consists of 



an eversible gland, composed of hypodermic cells, usually retracted 

 by a slender muscle and with an efferent passage, but the glands 

 vary greatly in shape and structure in different insects. In some 

 cases these foetid glands appear not to be the homologues of the coxal 

 glands, but simply dermal glands. 



These repugnatorial glands are of not infrequent occurrence in the 

 lower or more generalized winged insects, and in situation and ap- 

 pearance are evidently the homologues of the coxal glands of the 

 Symphyla and Synaptera. 



Foetid glands of Orthoptera. In the ear- wigs (Forficula and Cheli- 

 dura) Meinert has detected a pair of what he calls foetid glands at 

 the posterior margin of the dorsal plates of the 2d and 3d abdominal 

 segments. 



Vosseler also describes the same glands as consisting of a retort- 

 shaped sac, in whose walls are numerous small hypoderrnal cells and 

 large single glandular cells provided with an efferent passage, the 

 fluid being forced out by the pressure of the dermal muscles, one 

 acting specially to retract the gland. The creature can squirt to a 

 2u 



