A I, A II, A III. Diagrammatic sections of Amphioxus in its early stages (founded upon Kowalevsky's observations).
B I, B II, B III. Diagrammatic longitudinal sections of an hypothetical animal, intermediate between Amphioxus and Batrachians, in its early stages.
C I, C II, C III. Diagrammatic longitudinal sections of Bombinator igneus in its early stages (founded upon Götte's observations). in C III the neural canal is completed, which was not the case in B III. The epiblast in C III has been diagrammatically represented as a single layer.
D I, D II, D III. Diagrammatic longitudinal sections of an animal, intermediate between Batrachians and Selachians, in its early stages.
E I, E II, E III. Diagrammatic longitudinal sections of a Selachian in its early stages.
E´. Surface view of the yolk of a Selachian's egg to shew the manner in which it is enclosed by the Blastoderm. The yolk is represented yellow and the Blastoderm blue.
F I, F II, F III. Diagrammatic longitudinal sections of a Bird in its early stages.
[19] From the Quarterly Journal of Microscopical Science, Vol. XV. 1875.
[20] I have been able to make at Naples observations which confirm the account of the invagination of Amphioxus as given by Kowalevsky, though my observations are not nearly so complete as those of the Russian naturalist.
[21] Paper No. V, p. 82 et seq. in this edition.