PREFACE. V 



establishment of a completely new system of Mor- 

 phology. My object will have been fully attained if 

 I have succeeded in adding a few stones to the edifice, 

 the foundations of which were laid by Mr Darwin in 

 his work on the Origin of S'pecies. 



1 may perhaps call attention to one or two special 

 points in this work which seem to give promise of 

 further results. The chapter on the Development of 

 the Spinal and Cranial Nerves contains a modification 

 of the previously accepted views on this subject, which 

 may perhaps lead to a more satisfactory conception 

 of the origin of nerves than has before been possible, 

 and a more accurate account of the origin of the 

 muscle-plates and vertebral column. The attempt to 

 employ the embryological relations of the cephalic 

 prolongations of the body-cavity, and of the cranial 

 nerves, in the solution of the difficult problems of the 

 Morphology of the head, may prove of use in the line 

 of study so successfully cultivated by our great English 

 Anatomist, Professor Huxley. Lastly, I venture to 

 hope that my conclusions in reference to the relations 

 of the sympathetic system and the suprarenal body, 

 and to the development of the mesoblast, the noto- 

 chord, the limbs, the heart, the venous system, and 

 the excretory organs, are not unworthy of the attention 

 of Morphologists. 



The masterly manner in which the systematic 

 position of Elasmobranchs is discussed by Professor 

 Gegenbaur, in the introduction to his Monograph on 

 the Cranial Skeleton of the group, relieves me from 

 the necessity of entering upon this complicated question. 

 It is sufficient for my purpose that the Elasmobranch 

 Fishes be regarded as forming one of the most primi- 

 B. h 



