Spiders and Their Near Relatives 



The transformations have been described by Metchnikoff ('71), 

 Bouvier ('96), and Barrois ('96). 



Behind the opening of the reproductive organs there are two 

 median papillae through which glands open, one at the anterior 

 edge of the second abdominal segment and one in the corresponding 

 place on the third abdominal segment. These were formerly 

 believed to be silk organs; but the glands are now regarded as 

 cement glands, which secrete the substance with which the eggs 

 are fastened to the mother. These 

 glands appear to develop periodically 

 (Bernard '93). 



In the males there is borne by the 

 first abdominal segment a pair of re- 

 markable structures known as the ram's- 

 horn organs. They are situated under 

 the genital operculum, close to the 

 genital aperture. In Fig. 42 the tips 

 of these organs can be seen through 

 the genital operculum; but they may be 

 extended to great length, reaching to 

 either the front or the hind end of the 

 body as shown in Fig. 47 from Simon 



('79)- 



The function of these organs has 



not been determined. Menge ('55) who 



first described them, believed that they 



Fig. 47. VEN- 

 TRAL ASPECT 

 OF CHELIFER 

 SHOWING THE 

 RAM'S-HORN 

 ORGANS EX- 

 PANDED 



\ 



J 



were sexual organs; but Croneberg 



('88) and Bernard (93) suggest that they are respiratory. 



1 he true silk glands were discovered by Croneberg ('87). 

 They are situated in the cephalothorax and open through a group 

 ol minute apertures near the tip of the movable finger of the 

 chelicera, in the same position as the opening of the poison gland 

 of spiders. In those forms in which the spinneret is long and 

 branched the openings of the silk ducts are on the tips of the 

 branches; in Obisium they open on a blunt prominence, which 

 may be regarded as a rudiment of a spinneret ; in this case according 

 to Bernard ('93a) there are about seven of these ducts in each 

 chelicera. 



The silk spun by the chelicera? is used for the formation of 

 a web or a cocoon in which the pseudoscorpion retreats during 



43 



