in the Animal Kingdom. 



Fig. 8. 



fdeal Transverse Section of a Vertetwated Animal, to shew the Type of tht 



Extremities. 



a Stem of the vertebral column. 

 6 Arches of the Vertebrae. 

 e Ribs. 



* Ven't'ral } radical portion. 

 Under f middle portion. 



A Terminal portion. 

 h' Terminal portion as a Fin. 



(This fig. is taken from Von Bar.) 



In the substance of the fleshy portion of the Lamina dorsalis 

 and ventralis of each side, there is formed a series of osseous arcs 

 (fig 8, d e), constituting the radical portion of the extremities, of 

 the superior maxillae, &c. ; and from a point near the middle of 

 each arc, there issues a process corresponding to the middle (fg) 

 and terminal (/*) members of the latter. Now, it is obvious, 

 that with this common origin, and the same manner of develop- 

 ment, corresponding parts in different animals of the Class Ver- 

 tebrata, whether arms, legs, wings, fins, maxillae, &c. are likely 

 to retain a general resemblance ; though the absence of the middle 

 members, or modification of the whole extremity, &tc. may ren- 

 der them very dissimilar in their details. 



Corresponding parts of structure may, however, in different 

 animals, perform very, different functions. Thus, besides the 

 extremities just mentioned, many other examples might be 

 given ; such as a fact pointed out by Geoffrey St Hilaire, that 

 certain parts of the hyoid bone in the Cat, correspond to the 

 styloid processes of the temporal bone in Man ; and the different 

 functions of the generative organs in the two sexes, afford a sliil 

 more remarkable example. 



It has thus been shewn, why corresponding organs may rv- 



VOL. XXII. NO. XL1II. JANUARY 1837. I 



