448 INVERTEBRATE MORPHOLOGY. 



in other forms also, though it is probable that two glandular 

 tubes which open to the exterior on the sides of the cephalo- 

 thorax have in some forms been mistaken for these organs. 

 Odoriferous glands are also found in the abdomen of some 

 forms, and so-called salivary glands occur in connection with 

 the pedipalps. 



The nervous system shows a marked concentration of the 

 postoral ganglia, a single pair only remaining separate from 

 the fused mass formed of the remainder. The majority of 

 forms possess but a single pair of eyes on the dorsum of the 

 cephalothorax, but in Gibbocettum two lateral pairs are 

 found. 



Coxal glands have been described in connection with the 

 coxal joints of the third pair of legs and have been observed 

 to communicate with the exterior, differing therefore from 

 those of other Arachnoids in being functional in the adult. 

 The reproductive organs are unpaired, a condition which 

 results from the fusion of originally paired structures, and 

 the genital pore lies in both sexes at the junction of the 

 cephalothorax and abdomen or on the first abdominal seg- 

 ment. The vasa deferentia and oviducts are paired, each of 

 the former communicating with a protrusible penis, while 

 similarly each oviduct unites with a long protrusible ovipositor. 



Certain genera such as Leiobunum (Fig. 205), Plialangium, 

 and Opilio, are exceedingly common, and to them the terms 

 Harvest-men, Harvest-spiders, or Daddy Longlegs are popu- 

 larly applied. Other forms, such as Gonyleptus, with spiuose 

 pedipalps, are tropical in habitat, while OyphopMhcHmus and 

 Gibbocellum have a limited distribution, and on account of the 

 many differences of structure which they present when com- 

 pared with other forms are sometimes grouped together to 

 form a separate order. It is to be noted especially that these 

 two forms possess upon the second abdominal segment a pair 

 of wartlike elevations at the summit of which the ducts of 

 numerous spinning-glands open. 



6. Order Aranese. 



The order Aranese includes a large number of forms 

 possessing very definite characteristics. The cephalothorax 



