NERVES OF MAMMALIA. 165 



other words, that the same bone or osseous element may be pointed 

 out from the Cod-fish up to Man. But at this point the above 

 question may be met by the averment, that it need not be asked : 

 that there is no ground for homological generalisation higher 

 than the special one. Such anatomists rest on the step beyond 

 which Cuvier refused to pass. With him parts were homologous 

 because they served similar purposes, or were under like teleo- 

 logies! conditions of existence. Neither the final nor the me- 

 chanical causes of separate basi-, ex-, and super-occipitals, of basi- 

 and ali-sphenoids, parietals, &c. in the skull of the foetal Bird or 

 Kangaroo, have been explained l ; and as I am unable to conceive 

 of them, and am in no wise helped by the averment of inhe- 

 ritance, I retain my conviction that the basilar process of the 

 human occipital bone is the centrum of the hindmost cranial ver- 

 tebra ; having, moreover, traced the scapular arch and appendage 

 to its extreme of simplicity in Protopterus and Lepidosiren, I 

 accept the light which such condition throws upon its general ho- 

 mology, as the haemal arch of the same (occipital) cranial vertebra. 



If there be cartilaginous fishes that combine a foetal gristly con- 

 dition of skull with a maximised development of scapular append- 

 age, I conclude that the backward displacement of the sustaining 

 arch, from its type-position, is a consequence of such development, 

 and prefer to allow my reasoning as to the nature of a limb to be 

 guided by the state and conditions of such appendage in the verte- 

 brate series, rather than by the state of the cranium in one part 

 thereof. It is not probable that the pectoral fin of Shark or Skate 

 shows the condition under which the appendage of the scapular 

 arch first appeared in fishes. 2 



On laying open the neural canal, and exposing the myelon by 

 slitting up and reflecting the ' dura-mater,' as in fig. 135, the roots 

 of the nerves are seen, which go off in lateral pairs, and escape at 

 the intervals of the vertebrae: they are called the ( spinal' or 

 ' myelonal' nerves. One bundle of the radical filaments proceed 

 from the antero-lateral, the other bundle from the postero-lateral 



1 Messrs. Seeley and Spencer dispute the priority of such explanation and don't 

 give it. xci" and xcn." 



2 Respect for the conductors and editor of lxxv has led me into the above digres- 

 sion; and as they meet what they consider the 'main defect ' (ib. p. 123) of the present 

 work by an ' argumentum ad verecundiam,' I would observe that the individual who 

 first perceives, or discovers, the general homology of the basioccipital, the scapula, or 

 other part of the hindmost segment of the skull of a cod-fish, puts himself in advance of, 

 and more or less in antagonism with, others. If his perception be true, but not accepted, 

 it is not his fault that ' he be right and everybody else wrong.' Such a state of things 

 has happened more than once in the history of science, but it is happily transitory; the 

 many moving one-ward, the one onward. 



