THE ARCHETYPE 107 



clavicle is anterior to the coracoid " its anterior position 

 to the coracoid in the air-breathing Vertebrata is no valid 

 argument against the determination, since in these we 

 have shown that the true scapular arch is displaced back- 

 wards " (On the Nature of Limbs, p. 63, London, 1849). In 

 the pelvic girdle the ilium corresponds to the scapula, 

 the ischium to the coracoid, the pubis to the clavicle. Hence 

 the ilium is a pleurapophysis, the ischium and pubis 

 are both haemapophyses. The fore-limb is the developed 

 " appendage " of the occipital vertebra, the hind-limb the 

 developed " appendage " of the pelvic vertebra. They are 

 serially homologous with, for example, the uncinate processes 

 of the ribs in birds (see Figs. 5 and 6). The fore-limb is a 

 simple filament in Lepidosiren, and presents few joints in 

 Proteus and Amphimna ; in other air-breathing Vertebrates 

 it shows a more complete development, the humerus, radius 

 and ulna, and the bones of the wrist and hand becoming 

 differentiated out. 



As the fore-limb is equivalent to a single bone of the 

 archetype, it is said to be, in its developed state, " Ideologically 

 compound " (p. 103). 



Since in the archetype every vertebra has its appendage, 

 more than two pairs of locomotory limbs might have been 

 developed. " Any given appendage might have been the 

 seat of such developments as convert that of the pelvic arch 

 into a locomotive limb; and the true insight into the general 

 homology of limbs leads us to recognise many potential 

 pairs in the typical endoskeleton. The possible and conceiv- 

 able modifications of the vertebrate archetype are far from 

 having been exhausted in the forms which have hitherto 

 been recognised, from the primaeval fishes of the palaeozoic 

 ocean of this planet up to the present time" (p. 102). It is 

 not of the essence of the vertebrate type to be tetrapodal. 



In determining homologies Owen remained true to 

 Geoffrey's principle of connections. Speaking of an attempt 

 which had been made to determine homologies by the mode 

 of development, he writes, " There exists doubtless a close 

 general resemblance in the mode of development of homo- 

 logous parts ; but this is subject to modification, like the 

 forms, proportions, functions, and very substance of such 



