PLEXUS AND SACRAL VERTEBRAE OF LIZARDS. 515 



Professor Hoffman 1 finds the sciatic nerve of the Chameleon to be formed by four roots, 

 having, in addition to those given by Gegenbanr, a postsacral root also, formed by a 

 branch from the first postsacral nerve. He also represents the nerve formed by branches 

 from the second and third presacral nerves (and thus having but two roots) as dividing 

 into two important branches, one the obturator nerve, the other the crural. 



In our specimen of Chamcsleo vulgaris we found that the sciatic nerve might be said 

 to have either three or four roots, according as the branch (41 a) connecting together 

 the first and second postsacral nerves should be considered a branch going from the 

 former to the latter, or from the second postsacral nerve to the first one. But our 

 specimen differed importantly both from the descriptions of Gegenbaur and Hoffman in 

 that, in the first place, the crural (15) and obturator (5) nerves were formed by three 

 roots instead of two, and, in the second place, that the position of all the roots of the 

 sciatic and crural nerves was different. 



According to both Gegenbaur and Hoffman the sciatic nerve in this animal is formed 

 by the intersacral and the two presacral nerves, with or without the addition of fibres 

 from the first postsacral nerve, while of these roots the first presacral is the largest. 

 We, however, found the sciatic nerve (33) to be formed by the intersacral (29), first 

 presacral (12), and first postsacral (30) nerves ; while of these roots the intersacral was 

 the largest. Again, both Gegenbaur and Hoffman found the first presacral nerve to be 

 undivided and to go wholly to the sciatic plexus, while we found the first presacral nerve 

 to bifurcate, one branch (12) descending to the sciatic, the other (11) ascending to the 

 lumbar plexus. 



According to both Gegenbaur and Hoffman this lumbar plexus is formed from the 

 second and third presacral nerves, while we found it to be made up from the firsts 

 second, and third of these nerves (2, 9, and 11). Having united into a single trunk, we 

 found that this trunk almost immediately divided (as represented by Hoffman) into the 

 crural (15) and (5) obturator nerves, whereof the latter traversed the small pubic 

 foramen, called obturator foramen by Professor Hoffman 2 . 



Lacerta viridis. (Plate LXVI. fig. 2.) 



Professor Gegenbaur represents the sacral plexus of Lacerta as formed of three roots, 

 the middle one of which (that formed by the first presacral nerve) is the largest, and 

 sends no branch to the lumbar plexus; while the second presacral nerve bifurcates, 

 sending one branch to the last-mentioned plexus and one to the sacral plexus. The 

 lumbar plexus is formed by but two roots, one being part of the second presacral nerve, 

 and the other part of the third presacral nerve. 



Professor Hoffman 3 quite agrees as to Lacerta viridis with Professor Gegenbaur, save 

 that he represents no nervous connexion whatever between the intersacral nerve and the 

 first postsacral. 



In one specimen of this species we found four roots to the sciatic nerve, there being a 

 distinct contribution to it from the first postsacral. Moreover we found as many as 

 three roots to the lumbar plexus, the fourth presacral nerve (2) concurring in its 



1 L. c. pp. 174, 175, fig. 6. 2 L. c. tab. xi. figs. 9 and 10, fo. 3 L. c. pp. 175, 176, fig. 9. 



