42 THE STRUCTURE AND LIFE OF BIRDS chap. 



may develop into very birdlike creatures, and so, that 

 birds themselves may have had a reptilian origin. 



In the Secondary or Mesozoic period, there were 

 upon the earth Pterodactyls or wing-fingered animals, 

 also known by the name of Ornithosaurians or Bird- 

 lizards. Some very perfect specimens of these have 

 been found in the lithographic-stone at Solenhofen 

 in Bavaria. England and America have produced 

 pterodactyl bones and almost complete skeletons, 

 the latter country some of enormous size, and thanks 

 to the labours of great anatomists — among them Pro- 

 fessors Huxley and H. G. Seeley and Sir Richard Owen 

 — we now understand a great deal about these flying 

 reptiles, and can form a fair notion of how they lived. 



On looking at a restoration of one of these ptero- 

 dactyls, one's first thought is, that it is their wings 

 which prove them to be nearly related to birds. This 

 requires to be closely looked into, and what was said 

 above about analogy and homology must be borne in 

 mind. The wings of birds and pterodactyls are similar 

 in function, but in their structure they are very different. 

 They are analogous but not homologous. A bird's 

 wing contains three fingers. The first is very small, 

 the second is far the biggest and strongest, and to it the 

 third is immovably attached. Dr. Hurst l has tried to 

 show from the evidence of the Berlin Archseopteryx 

 that these three digits are not the first three, but that 

 the two united ones are the fourth and fifth. For this 

 view, as far as I can see, no evidence is to be found in 

 the Berlin Archaeopteryx or anywhere else. But when 

 he maintains that the generally accepted view, that the 

 1 Natural Science, October, 1893. 



