4 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



common aim inspires us all— to define the action of 

 organic forces, to reduce order out of apparent chaos, to 

 peer as deeply as we can into the well of Truth. 



It is with special pleasure that I come before you 

 to-day. It is a particular gratification to an anatomist 

 to have the opportunity of discussing with a sympathetic 

 audience some of the difficulties and puzzles that confront 

 him in his special department of Biology. 



The study of animal morphology is overshadowed by 

 the doctrine of evolution, and the theory must admittedly 

 be tested and tried by the searching light of structure and 

 development. Palaeontology looks ever backward. 

 Functions may change, and be transferred to structures 

 of an alien pattern. Structure is always reliable. The 

 matter of the origin of species cannot be said to be con- 

 clusively settled. There are many points in vertebrate 

 anatomy which bear upon it, and it is to a few of these 

 points that I wish to direct your attention for a while 

 to-night. 



The thought has occurred to me that the question of 

 the individuality, or the transmutability of species might 

 be settled definitely by a study of some of the lowest forms 

 of life, such as Bacteria ; but if after the exhaustive study 

 of such primitive forms the subject is still baffling, how 

 much greater difficulty does it present when we are con- 

 cerned with complex and highly organised animals, such 

 as Vertebrates. 



Vertebrate Architecture. 



In any study of comparative anatomy our primary 

 object is to decide upon the principal features, the plan 

 of architecture of the animals in question. 



Among vertebrate animals obviously the most 

 characteristic features are a tubular structure, bilateral 

 symmetry and segmentation. 



