112 BRITISH TYROGLYPHimE. 



such as Lang and others, consider that this very fact 

 prevents the mandibles of insects and Arachnids being 

 considered homologous ; (2) that Winckler* stated that 

 in Gamasus he had found the roots of the mandibular 

 nerves in the sub-oesophageal ganglion, and that they 

 passed right through the substance of the supra-ceso- 

 phageal ganglion before emerging from its dorsal 

 surface. I have a very high opinion of Winckler's 

 general accuracy in this paper, but I have not ever been 

 able to confirm this statement, although I have great 

 numbers of successful serial sections through the brains 

 of Gramasids of various species cut in all directions ; (3) 

 that although the mandibular (cheliceral) nerves arise 

 from the supra-oesophageal ganglion in adult Arach- 

 noidea, yet that in some at least of the creatures 

 belonging to that class, the ganglia from which these 

 nerves spring in the embryo are not supra-oesophageal, 

 but work upward in the course of development. 



As above stated, I can hardly think that Nalepa is 

 correct in saying that the palpal nerves arise from the 

 supra-oesophageal ganglion. 



As so little is really known of the course of the 

 nerves in the Tyroglyphidae it may possibly be useful 

 just to state what nerves I found arising from the 

 brain in Bdella. They were from the supra-oesopha- 

 geal ganglion, the azygous pharyngeal nerve, and 

 three pairs of paired nerves, viz. (1) the mandibular 

 nerves ; (2) a thin pair innervating the dorso-ventral 

 muscles near the rostrum ; (3) the optic nerves : from 

 the sub-oesophageal ganglion seven pairs of nerves, 

 viz. 1, the palpal nerves; 2 to 5, the leg-nerves; 6, 

 the genital nerves ; 7, a thin pair, innervating the 

 dorso-ventral muscles in the centre of the body. 



OEGANS OF SPECIAL SENSE. 



This must necessarily be a very short section of the 

 anatomy, for the known organs of special sense in the 



* " Anatomic der Gamasiden," in ' Arb. Inst, Wion,' T. vii, Heft 3, 

 pp. 317354. 



