304 llcvr J. Wagiicv on the 



Weissenborn {he. cit. pp. 115-110) disafj^rces witli the 

 opinion of Schinikewitsch, since with the help of it it is 

 impossible to explain the dendriform tracheiB of the Solifuq;?©, 

 and he proposes another explanation. I may also add that 

 if the Solifugfe are less modified forms than the Spiders we 

 must, on the other hand, not lose sight of the fact that in the 

 same forms of Arachnids we meet with not only lung-shaped 

 and fascicular tracheae at the same time, but also both 

 distinctly developed kinds of fascicular tracheae [e. (j. in Gihho- 

 cellu77i, according to the description of Stecker (No. 61)*]. 

 According to Weissenborn the whole of the respiratory organs 

 of Arachnids have arisen from primitive unbranched short 

 tracheal tufts, from which in one direction dendriform tracheal 

 tuffs, in another tubular tracheae with considerable diminution 

 in the number of the stigmata, and in a third lungs were 

 developed. From this it may be inferred that in the opinion 

 of the author the trachea? of the Spiders with two lungs and 

 the posterior lungs of those provided with four have deve- 

 loped independently of each other from the primitive tracheal 

 tufts of the ancestral form — a theory which, according to 

 I^ocock's paper (No. 54), and since the four-lunged Hypo- 

 chilus was recognized as a " Dipneumon," is wholly im- 

 probable. 



A peculiar view as to the respiratory organs of Arachnids 

 is represented by Bernard (No. 6). This author regards the 

 tracheae of the Acarina as the most primitive type ; the ex- 

 clusive presence of these organs in the Acarina is in accord- 

 ance with his theory that the Acarina are a fixed larval stage 

 of the Arachnids. I shall discuss the theory just alluded to 

 later on. The presence of the tubular trachea in the Pha- 

 langidse is explained by the very early separation of the latter 

 from the main stem of the Arachnid class ■ the Solifugje 

 possess the same tracheae, since they are very near akin to 

 the primitive type of the Arachnida ; the ChernetidEe lastly 

 must be separated into a special group. From the tubular 

 tracheai have been developed the " fan-tracheaj " (" Fiicher- 

 tracheen," " book-leaf tracheae " of Bernard, No. 7, p. 521). 

 This is Bernard's view. In connexion with the term " tubular 

 tracheae," he nowhere states which of the tubular tracheae, 

 the fascicular or the dendriform, he regards as the more 

 primitive f ; he simply contrasts the tube-tracheee with the 



• Stecker (he. cit. p. 339) compares the posterior tracheal tufts in 

 Gilhocellum with the abdominal tracheal branches in Phalangium. 



+ [This paper was evidently written before the author had seen Ber- 

 nard's " Notes on the Chernetidse/' Journ. Linn. Soc, Zool. xxiv. pp. 410- 

 430, pb. xxxi. and xxxii. (Nov. 1893), in which this question is more 

 fully dealt with. — Tra>'sl.] 



