History of a transient nervous apparatus in certain Ichthyopsida. 421 



Plate 24. 



Fig. 41. A compound sub-epiblastic nerve, partly made up by a 

 ganglion-cell almost central in position, and partly by applied ganglion- 

 cells. Embr. No. 430, 14,5 mm. Magnif. 225 X I- 



Fig. 42. A remarkable "plexus" of ganglion-cells and fibres arching 

 over the myotome, from the ganglion-cell nearest the cord a nerve fibre 

 reaching to the centre. The drawing is a combination of two con- 

 secutive sections. Embr. No. 192 (see Fig. 38). Magnif. 500 X I- 



Fig. 43. From the same embryo as the preceding. A bipolar cell 

 with processes towards the centre and over the myotome apex. Magnif. 

 as beifore. 



Fig. 44. Five central ganglion-cells, but, more particularly, a nerve- 

 fibre formed by a reduced ganglion-cell. Embr. No. 219, 37,5 mm. Magnif. 



225 X I _ 



Fig. 45. From the same embryo as Fig. 21. The figure shows to 



the right a ganglion-cell lying in the cutis-layer of the myotome, as 

 also two curiously constructed sub-epiblastic nerves. Magnif. 225 X f- 



Fig. 46. A bipolar transient ganglion - cell with its two nerve- 

 processes. Embr. No. 201, 25 mm. Magnif. (Seibert 4 mm) 225 X I- 



Fig. 47. From the same embryo. Three central ganglion-cells, 

 with capsule-cells (c. c). One ganglion-cell to the right has spun a 

 long sub-epiblastic fibre. Magnif. as before. 



Fig. 48. A transient nerve-fibre, with applied ganglion-cell, piercing 

 the myotome. Embr. No. 441, 21 mm (chrome-osmic-acetic acid pre- 

 paration). Magnif. 500 X f- 



Fig. 49. A transient nerve-fibre with nerve-forming nuclei. Embr, 

 No. 219 (see Fig. 44). Magnif. 225 X f- 



Fig. 50. A fine example of a nerve fibril spun by a central cell. 

 Embr. No. 453 (preparation sublimate-bichromate-osmic mixture). Magnif. 

 225 X I- 



Fig. 51. A remarkable chain of transient ganglion-cells. Embr. 

 No. 180, 12 mm. 111 somites. Magnif. (Seibkrt 4 mm) 225 X I- 



Fig. 52. Applied ganglion-cells in the course of forming fibres in 

 two directions. Embryo and magnif. as before. 



Fig. 53. A group of central ganglion-cells. Also one commencing 

 to spin a fibre. Embr. and magnif. as in Fig. 51. 



Fig. 54. A ganglion-cell near the myotome with the fibre of a 

 central ganglion-cell applied to it. Embr. as before. Magnif. 500 X I- 



Fig. 55. From the same embryo as the preceding. To the left 

 a nerve-process reaching to the myotome, in the centre a fibril extending 

 to the epiblast, and near it a wandering transient ganglion-cell (w. ^?. Cj. 

 To the right a wandering cell {w. gl. c) on cells of the spinal ganglion. 

 In connection with the central cells there are now capsule-cells. 

 Magnif. 500 X I- 



Fig. 56. Two transient ganglion-cells lying in the cutis layer of 

 the myotome. No nerve was seen in connection with either of them. 

 Embr. No. 189, 20—21 mm. Magnif. 225 X I- 



28* 



