188 Dr. M. Laurie on the 



pair of lung-books (tenth segment), as in Parabuthus (fig. 1), 

 and a position forward in the second free segment, as in Scorpio 

 fulvipcs (fig. 3). In Vfjovis it is even furtlier forward. 



The nerve from it, however, passes always behind the 

 dorso-ventral muscle of the fourth mesosomatic (tenth) seg- 

 ment. About the level of this muscle it divides into two 

 branches, of which the anterior runs out to the body-wall, 

 while the posterior runs back to the lung-book in the fifth 

 mesosomatic (eleventh) segment. 



The second ganglion may lie in the sixth mesosomatic 

 (twelftli) segment, as in Parahuthus (fig. 1), or it may lie 

 forward towards the front of the fifth mesosomatic (eleventh) 

 segment, as in Palamnmus (fig. 2) and Vejovis. The 

 nerve from it runs behind the dorso-ventral muscle of the 

 fifth mesosomatic (eleventh) segment, and in front of that of 

 the twelfth segment, divides into two, and the posterior branch 

 goes to the last lung-book. 



The third ganglion may lie well back in the first meta- 

 somatic (thirteenth) segment, as in Scorpio (fig. 3), or forward 

 in the last mesosomatic (twelfth) segment, as in Palamnceus 

 (fig. 2). The nerve from it runs either backward or forward, 

 according to the position of the ganglion and of the dorso- 

 ventral muscle of this segment, in front of which it passes. 

 I have never been able to trace it to the last pair of lung- 

 books, but it always goes to the muscles of the segment 

 (thirteenth) to which it belongs. It does not divide into two 

 branches as those in front of it do. 



The four ganglia behind this supply each one of the meta- 

 somatic segments except the last ganglion, which innervates 

 the last two segments and the telson. 



The nerves from the prosomatic ganglion to the first and 

 second lung-books have a course much like the nerves from 

 the first two ganglia. They pass respectively behind the 

 dorso-ventral muscles of the second mesosomatic (eighth) and 

 third mesosomatic (ninth) segments. Each divides into two 

 branches — an anterior body-wall branch and a posterior 

 branch to the lung-books. 



In Opisthophthalmus and probably in others, a fine nerve 

 runs longitudmally down the mesosoma on each side (fig. 4, 

 l.n.). It passes in each case under the body-wall branch of 

 the nerve and over the lung-book branch. It is connected 

 with each of the segmental nerves by a fine branch arising 

 from the nerve before it dividesinto two branches (segment 10), 

 from the body-wall branch alter the division (segment 11), 

 or from the point of division of the nerve (segment 12). I 



