TABLE OF CONTENTS. 



Page. 



lutroductory 1 



I. — Termiuology 2 



II. — The theory of the developmeut of the median fins 5 



III. — On the degeneration of the posterior part of the axial skeleton of fishes. 11 

 IV. — The serial homology of the hypaxial and epaxial elements of the caudal 



fiu 19 



V. — Development of the median and paired fins and the effects of concres- 

 cence 23 



VI. — On the protopterygiau stage of development of the rays in the fins 33 



VII. — What is it that constitutes a fin- ray ? 37 



VIII. — Special modifications of the dev^elopment of the fins 41 



IX. — On the transformations of the tail of Mola ,. 47 



X. — Discussion of the serial homology and the influence of h'eredity on the 



development of continuous fin-folds 60 



XI. — The tendency of heterocercy towards gephyrocercy 69 



XII.— On the influence of muscular metamerism on the development of the 



axial and appendicular skeleton of fishes 73 



XIII. — The mesenchyme of vertebrated embryos 7G 



XIV. — On the stimuli determining the outgrowth of the lower lobe of the 



caudal tin 77 



XV. — On the movements of parts of living bodies considered as the causes of 



morphological differentiation 85 



XVI. — Lamarck's share in the development of tlie principles of dynamical evo- 

 lution : . . 95 



XVII. — A statement of some objections and concluding remarks 103 



127 



1107 



