The section contains an anterior root, which takes its origin at a point opposite the interval between two posterior roots.
The white matter has not been very satisfactorily represented by the artist.
Figs. I I, I II. Two sections of a Pristiurus-embryo somewhat older than H. Camera. (Zeiss CC ocul. 1.)
The connective-tissue cells are omitted.
Figs. I a, I b, I c. Three isolated cells from the ganglion of one of the posterior roots of the same embryo.
Figs. K I, K II. Two horizontal longitudinal sections through an embryo in which the external gills have just appeared. K I is the most dorsal of the two sections. Camera. (Zeiss CC ocul. 1.)
The sections shew the relative positions of the anterior and posterior roots at different levels.
pr. posterior nerve-rudiment. ar. anterior nerve-rudiment. sp.c. spinal cord. n.c. neural canal. mp. muscle-plate. mp´. first-formed muscles.
Fig. L. Longitudinal and vertical section through the trunk of a Scyllium-embryo after the external gills have attained their full development. Camera. (Zeiss CC ocul. 1.)
The embryo was hardened in a mixture of chromic acid and osmic acid.