Complete List of Reference Letters.
al. Alimentary tract. ao. Aorta. c. Connective tissue. cav. Cardinal vein. ch. Notochord. ep. Epiblast. ha. Hæmal arch. l. Liver. ll. Lateral line. mc. Mucous canal of the head. mel. Membrana elastica externa. mp. Muscle-plate. mp´. Muscles of muscle-plate. na. Neural arch. nl. Nervus lateralis. rp. Rib process. sd. Segmental duct. sh. Sheath of notochord. spc. Spinal cord. spg. Spinal ganglion. syg. Sympathetic ganglion. um. Ductus choledochus. v. Blood-vessel. var. Vertebral arch. vb. Vertebral body. vcau. Caudal vein. vin. Intestinal branch of the vagus. vop. Ramus ophthalmicus of the fifth nerve. x. Subnotochordal rod.
Fig. 1. Section through the anterior part of an embryo of Scyllium canicula during stage L.
c. Peculiar large cells which are found at the dorsal part of the spinal cord. Sympathetic ganglion shewn at syg. Zeiss A, ocul. 1.
Fig. 2. Section through the lateral line at the time of its first formation.
The cells marked nl were not sufficiently distinct to make it quite certain that they really formed part of the lateral nerve. Zeiss B, ocul. 2.
Figs. 3a, 3b, 3c, 3d. Four sections of the lateral line from an embryo belonging to stage L. 3a is the most anterior. In 3a the lateral nerve (nl) is seen to lie in the mesoblast at some little distance from the lateral line. In 3b and 3c it lies in immediate contact with and partly enclosed by the modified epiblast cells of the lateral line. In 3d, the hindermost section, the lateral line is much larger than in the other sections, but no trace is present of the lateral nerve. The sections were taken from the following slides of my series of the embryo (the series commencing at the tail end) 3d (46), 3c (64), 3b (84), 3a (93). The figures all drawn on the same scale, but 3 a is not from the same side of the body as the other sections.
Fig. 4. Section through lateral line of an embryo of stage P at the point where it is acquiring an opening to the exterior. The peculiar modified cells of its innermost part deserve to be noticed. Zeiss D, ocul. 2.
Fig. 5. Mucous canals of the head with branches of the ramus ophthalmicus growing towards them. Stage O. Zeiss A, ocul. 2.
Fig. 6. Mucous canals of head with branches of the ramus ophthalmicus growing towards them. Stage between O and P. Zeiss a a, ocul. 2.