" wind-scorpions:' 337 



membranes were drawn into the body to form an Inter- 

 nal skeleton, the shape of which varies according to the 

 ways in which the component segments have coalesced. 

 A comparative study of these endoskeletal structures 

 and the different ways the segments have been knit 

 together shows this beyond dispute. In the Galeodidae, 

 in which the three posterior segments of the anterior region 

 remain free, the endoskeleton is limited to one single pair 

 of infoldines, viz., of the membrane between the third and 

 fourth rings. What is also important is that in Galeodes 

 this endoskeleton is clearly seen to be nothing but an in- 

 folding of the exoskeleton, whereas this origin is now difficult 

 to establish in the cases of the other Arachnids, specialisa- 

 tion having gone so far that the whole structure seems 

 more like a complicated framework of sinewy or tendinous 

 matter than a derivative of the chitinous cuticle by simple 

 infolding. This structure, then, is clearly due to the 

 differentiation of the body into two highly specialised 

 regions. 



These, then, are a few of the structural modifications 

 early initiated in the ancestral Arachnid and due to the 

 further specialisation of its adopted method of feeding. 

 These aofain have been carried further in various directions 

 by the different descendants of that ancestral form, the 

 modern Arachnids. In nearly all cases, it will have been 

 observed, the Galeodidse have retained the ancestral condi- 

 tions least changed. 



Before summing up these points in order to obtain a 

 rapid outline sketch of the ancestral form as here recon- 

 structed, another point of importance claims our attention. 

 The ancestral form must have been marvellously richly 

 supplied with glands of some simple kind from which the 

 many glands to be found in the Arachnida could be de- 

 duced. There are poison glands, glands for sticking the eggs 

 together (cement glands), and glands, the sticky secretion 

 of which, hardening as it is drawn out yields the silk for 

 cocoons and webs, and, lastly, stink glands. That all these 

 are derivatives of some common form of gfland is evident 

 to any one who makes a comparative study of them. The 



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