362 NATURAL SCIENCE. Nov., 



But while the facts are still a matter for controversy, the construction 

 of phylogenetic theories can but be speculative. 



Another order of arachnids — the Pedipalpida, or scorpion-spiders 

 — is, however, brought forward by Mr. Bernard in this last paper to 

 confirm his opinion. Examining dried specimens of Thelyphonidae 

 so that the ventral surface of the abdomen reflects the light, he finds, 

 outside the muscle impressions from the fifth to the eighth segment, 

 a paired series of scars, supposed to represent vestigial stigmata, and 

 of areas supposed to represent the flattened vestiges of vanished 

 limbs. Hence he concludes that the ancestor of the Arachnida pos- 

 sessed a pair of limbs and a pair of stigmata on every segment. 

 That a very remote ancestral form of the group possessed a long 

 series of paired limbs, functioning as breathing organs, is quite 

 possible ; but the fact that in primitive living terrestrial arachnids (the 

 scorpions), as well as in both living and extinct aquatic arachnids 

 (Luintlus and the Eurypterida), no breathing organs occur behind the 

 sixth abdominal segment, renders it highly probable that in the 

 immediate ancestors of the class the series had already become so far 

 reduced. 



In his researches upon the Chernetida (3), Mr. Bernard has paid 

 much attention to the glands. He confirms Croneberg's statement 

 that the spinning-glands are situated in the cephalothorax, wherein 

 they occupy a large space dorsally, and that their ducts open be- 

 hind the tips of the movable fingers of the chelicerae. The peculiar 

 comb-like structures on these fingers, generally known as flagella, 

 are, therefore, probably used in working up the silk. The glands, 

 opening by median papillae upon the second and third abdominal 

 segments, which were thought by some observers to produce silk, 

 are believed by Mr. Bernard to secrete cement for fastening the eggs 

 together. The coxal glands have openings on the hinder face of the 

 coxae of the third pair of legs. 



Opening on the first abdominal segment, beneath the genital oper- 

 culum in Chernetids, are a pair of curved conical tubes, with trans- 

 versely folded walls, known as " ram's-horn " organs. These are 

 said to occur only in the male, and being sometimes found evagi- 

 nated, were believed by Croneberg and Menge to have a reproduc- 

 tive function, although the former considered them homologous with 

 the tracheal tubes. Mr. Bernard has found these structures in one 

 of his specimens, and observing that they are surrounded with air- 

 chambers, concludes that their function is respiratory. He natu- 

 rally regards them as homologous with the tracheal tubes, and 

 expresses his belief that they represent the starting-point from which 

 tracheal tubes or tufts and lung-books have been elaborated. He 

 would thus find here another argument for the primitive nature of 

 tracheae with respect to lung-books. 



In a former review in Natural Science (vol. ii., p. 449) I 

 mentioned some well-knoAvn facts of comparative anatomy and 



