. ON THE SACBAL VEBTEBBJB OE LIZABDS. 371 



the nervous and osteological relations of any vertebra coustautly 

 agree with, the nervous and osteological relation of Man's first 

 sacral vertebra, the homology between such two parts may well be 

 taken as thereby established ; but if either of these sets of rela- 

 tions exhibit discrepancy, then of course such homology cannot be 

 considered satisfactorily determined. 



Nor can we justly set aside osteological in favour of nervous 

 resemblances if it should turn out that the nerves themselves ex- 

 hibit notable variations of conditions as we pass from one allied 

 form to another — a fortiori if there should be variations in this 

 respect even within the limits of a species. It might surely be anti- 

 cipated that more or less variation would be found to exist inner- 

 vous as well as in skeletal structures : and in the event of such anti- 

 cipations being justified, the determination of sacral homology must 

 depend upon a comparison of the values of the conflicting claims 

 of different degrees of resemblance in both the osseous and nervous 

 systems — unless we prefer to consider the osteological sacrum and 

 the nervous sacrum as two distinct structures, which may or may 

 not completely coincide, and may or may not widely diverge. 



The authors afterwards discuss the opinions held by Professor 

 Gregenbaur with regard to the pelvic relutious in birds and some 

 reptiles, also those of Professor Hoftmann concerning the lumbar 

 and sacral plexuses of Batrachians and Reptiles. 



Then follows an account of dissections of the Chameleon {Cha- 

 mcdeo vulgaris), the Green Lizard {Lacerta viridis), the common 

 Teguexin (Tem5 teguexin),t\ie Bearded Lizard {Orammatophora 

 harhata), the Agama colonorum, the Tuberculated Lizard {Iguana 

 tuberculata), and of the Monitor {M. arenaria). 



On these dissections are based some remarks on the general 

 condition of the nervous and osseous structures of the sacral region 

 in Lizards, according to their views and as compared with those 

 held by Gregenbaur and Hofiinann. To this succeed other chap- 

 ters devoted to a consideration of the sacral region of Batrachians, 

 to the sacral region of Mammals, and to the sacral region of Birds, 

 each discussed in a similar spirit. 



Their generalizations to the foregoing may be thus summa- 

 rized : — 



It appears, then, that in Lizards generally, the lumbar plexus 

 may be formed by from two to three roots, and that the most pre- 

 axial of these is here in advance of the fourth presacral nerve, 

 while the most postaxial root is never more postaxial than the first 



