ORIGIN AND SIGNIFICANCE OF SPINES 



85 



to Lucas, 43 a rapid change "takes place in the fore limb dur- 

 ing the growth of the bird, by which the hand of the nestling, 

 with its well-developed, well-clawed fingers, becomes the 

 clawless wing of the old bird with its abortive outer finger." 

 Similar claws or spurs occur on a number of other birds, 

 some having functional wings, as in the example just de- 

 scribed, and others having only vestiges of wings, as in the 

 Wingless Bird of New Zealand (Apteryx, figure 69). 



66 



67 



FIGURE 66. Female of LernceascuS nematoxys, a parasitic copepod ; showing 

 suppression of limbs. Enlarged. (After Glaus.) 



FIGURE 67. Horse-shoe Crab (Limulus polyphemus) ; showing telson spine 

 and abbreviated abdomen. Reduced. 



FIGURE 68. A Devonian phyllocarid (Echinocaris socialis) ; showing spiniform 

 telson and cercopods. 



FIGURE 69. Wing of Apteryx australis, X i- (After Romanes.) 



FIGURE 70. Skeleton of right fore limb of the Jurassic Dinosaur Iguanodon 

 bernissartensis ; showing partially suppressed first digit. X -fa. (After Dollo. 16 ) 



Another example may be taken from the Dinosaurian Rep- 

 tiles. The Jurassic genus Iguanodon, from England and 

 Belgium, belongs to a group (Ornithopoda) in which the 

 number of functional digits varies from three to five in the 

 manus, and from three to four in the hind foot. In this 

 genus the hind foot had three functional toes, representing 

 the second, third, and fourth of a normal pentadactyl foot. 



