1 68 



HIST. >kY OF I Ml'. HUMAN i:< >DY 



paialivrly ahnipt one, characteri/ed hv a rapid ad justment to 

 the need , oi .1 terrestrial life. It thus follows that the tniir.il i. .11 

 forms them-.elve-. niiisl have hceu put at a disadvantage when 

 in competition hotli with then immediate . !c -, nidanls, which 

 were better tittcd fur the laud, and with their immediate anres 

 tors, which had never lei! the \\..I<T, and their rapid extinction 

 WES a necessary consequence. Tin- deficiency in the historical 



record at the, place, however, has u<>i prevented speculation ,,n 

 this subject; on tlie contrary, it has proved an especially :>i- 



Fio. 43. Ditgrtmi llluitrsting iin- development <>i" tin- tm ikelelonj 



on (hat n! selachians, |.\ll<-r WlEDXRSHEIM,] In (.') ami ( ) 



the right M<I>- -.\i\\ . a lightly older stage than tin- Iri'i. 



1 1 active field for the anatomical philosopher, and the discus- 

 sion of some of the leading the.. lies of thi^ question \\ill he 

 COnsidned l.iithe! mi in the present chapter. 



A i<le fi.. in this pK.hlem, however, the history of (lie de- 

 velopment of the limh.s is hy no mean , i lear in other fCSpCCtS, 

 and although the faith in their o unplele h -niol. >:/>' tliroiiLdiuiit 

 [| Universal, the manner .1!' their dr\ el. .puieiil and (he relation 



of tin' various farms io one another cannot ie agreed upon. 



Embryology, \\hich is usually so sn ( ^e-.li\e. is praclicallv 



sileni here, since the record seems in :iii cases to he much 



ahhrcx ialed. The hest that can he dne, therefore, is (< 

 arrange :i se(|iience of adult farms \\hich si-em 1 slu>\v 

 liansitions frm .me t\|>e to another, paying as much regard 

 as possible I" the lines i.f de-rent a--, iudicah'd hv the other 



parts, in this \\a\ have been sketched tiu- histories which 



f"llo\\. and in readni! 1 this it must he i emeu il icred that a i' 



fi .nndcd ineiei\' on a succession of adult farms, and re 



