116 Dr Barry on the Unity of Structure 



The species which are common in the chalk and red crag are 

 very few when compared with those which are common to the 

 red crag and to the subsequent tertiary strata. In the latter 

 case, however, we have no means of ascertaining whether those 

 individual species which occur in separate formations existed 

 throughout distinct periods, or, like the fossils of the chalk, were, 

 by the natural process of degradation, removed from their ori- 

 ginal matrix, to be again entombed with the races of a more re- 

 cent epoch. Unless this difficult problem is solved, it is clear 

 that the application of the per-centage test may be attended 

 with the most fallacious results. JFo what extent erroneous con- 

 clusions may have already been formed, from the neglect of 

 those considerations so obviously necessary in the examination 

 of the crag, must be a subject for future investigation. Records 

 of General Science, No. xxiv. vol. iv. p. 465. 



On the Unity of Structure in the Animal Kingdom. By MAR- 

 TIN BARRY, M. D., F. R. S. E., M. W. S., late President 

 of the Royal Medical Society of Edinburgh. (Communi- 

 cated by the Author.) 



ALL finite existences presuppose design. This is a position 

 which, happily in the present day, we may assume. 



It has been usual to regard organic structure as manifesting 

 design, because it shews adaptation to the function to be per- 

 formed. It has also been suggested, that function may be 

 equally well considered as the result of structure. And, truly 

 so it may. Yet perhaps we are not required to shew the claim 

 of either to priority ; but may consider both structure and 

 function, harmonizing, as they always do, as having been si- 

 multaneously .contemplated in the same design. 



The object of the present essay, is to offer a few considera- 

 tions on structure only ; but the subject is so vast, and our li- 

 mits are so circumscribed, that these considerations must be of 

 the most general character. Yet some details on development 

 will be found indispensable. 



The^expression " organic structure," includes of course the 

 structure of what we call animals and plants. But, while both 

 are comprehended as beings contemplated in the same original 



