MOEPIIOLOGT or THE PEDIPALPI. 41 



the middle Hue, but in the Pedipalpi the appendages stretch 

 right across, as Macleod * suggested for spiders. 



This view differs from that which has recently been set forth 

 by Pocock f, who regards all the sclerites as sternites, and 

 considers that the ventral side of the second abdominal segment 

 has been crushed out by the great development of the first, which 

 extends so far back as to cover part of the third segment, 

 including the first pair of lung-books. The second sternite, that 

 of the third segment, has, according to him, been pushed back 

 by the same growth so as to cover the second pair of lung-books, 

 which belong to the fourth segment. 



Schizonotus, which I have unfortunately not had an oppor- 

 tunity of studying, is thus described by Pocock : — " There appears 

 usually to be a single pair of respiratory stigmata situated 

 behind the first sternite, as in Thelyplionus. The posterior pair 

 that are developed in Thelyplionus appear to be functionless, but 

 upon the third, fourth, and fifth sterna (morphologically the 

 fourth, fifth, and sixth), close to the posterior margin and behind 

 the muscular impressions, a pair of dusky patches are visible. 

 These appear to be some internal organs seen through the semi- 

 transparent cuticle, and I believe they are the homologues of the 

 three posterior pairs of lung-sacs of the Scorpion "J. If this 

 interpretation of these structures be correct, we have here traces 

 of the posterior abdominal appendages which have entirely dis- 

 appeared in Tlielyphonus and Phrynus. 



In Spiders the same arrangement is found as in the Pedipalpi. 

 This is particularly clear in that curiously primitive form Liphis- 

 iius, which has been recently described by Pocock §. In this 

 form the segmentation of the abdomen is marked on the dorsal 

 side by nine (Schiodte) chitinous tergites. On the ventral side 

 there are two large chitinous plates, the anterior of which covers 

 the genital aperture and the first pair of lung-books, while the 

 posterior covers the second pair of lung-books. These two 

 chitinous plates I would regard as the two appendages which are 

 found in the Pedipalpi. A further argument in favour of my 

 view is that the lung-books have been described as developing in 

 connection with the appendages of the second abdominal seguient. 



* Arch, de Biol. vol. v. 



t Ann. & Mag. Nat. Hist. vol. xi. 1893. 



I Tom. cit. p. 4. 



§ 6*2?. cfi!. vol. X. 1892. 



