PRESIDENT'S ADDRESS: xlv. 



the greatest interest both to the palaeontologist and the biologist. 

 Although all vertebrates have a general conformity in their 

 organisation, they show a great diversity of form, by which each 

 class and order can be clearly defined. The two upper vertebrae 

 of the cervical series of the vertebral column are designated the 

 axis and atlas. The centrum of the atlas is not joined to, but 

 remains either distinct from, or anchylosed to the axis. 

 The primitive position of the limbs of vertebrates is at right 

 angles to the axis of the body, and directed outwards. In the 

 majority of the Reptilia and Amphibia the limbs of the adults do 

 not depart very much from that direction. Changes of direction 

 are found with birds. With man the change is more divergent 

 from the types, for the axis of both the arm and the leg are 

 parallel to that of the body. The lowest vertebrates in the scale 

 retain throughout life their embryonic conditions. There is no 

 bone or true cartilage around the neural-arch, neither is there any 

 development of limbs ; worm-like they move by the flexion of 

 the body. The strength and rigidity of the spinal column 

 increases in proportion as the limbs are developed. They 

 never exceed four in number; in some cases two are absent, 

 and in others both pairs are wanting. The limbs of Fish, 

 Reptiles, and aquatic Mammals are modified for propulsion 

 through the water, and not for support. With terrestrial Quad- 

 rupeds, whether mammals or reptiles, the limbs are adapted for 

 the support of the body and for progression. With Birds the 

 anterior pair of limbs is developed into wings, by which the 

 body is more or less supported or propelled through the air. 

 Sight, smelling, hearing, and taste appear to be possessed by 

 most of the vertebrates. It is not uncommon for the visual 

 organs to remain undeveloped when the environments of the 

 animal render them useless, as in the case of those inhabiting 

 underground caves in which the rays of sunlight never enter, 

 or in the deep abysses of the sea. None of the limbs of 

 fishes are prehensile ; the mouth is propelled or guided by 

 them to their food, but the act of seizing it must be done by 

 the jaws; hence both the upper and lower are endowed with 



