336 JOHN BEARD, 



The transient ganglion-cells and their nerves first make their 

 appearance in the second slide of the series just slightly in front of 

 the pronephros. In several sections in front of the latter, though 

 there are transient ganglion-cells in or on the cord, there are pre- 

 sent no features worthy of special remark. When one examines sec- 

 tions well within the region of the pronephros, the ganglion-cells in 

 question are found to become abundant, and to project out towards 

 the apices of the myotomes, either as big bunches of cells, or as pro- 

 cesses spun out by centrally-lying cells, or finally as such processes 

 with applied ganglion-cells. From this series several sections are 

 figured on plate 22. In Fig. 13 four ganglion-cells {gl.c.c) form a 

 roof to the cord, one of them has spun out, and appears to be still 

 engaged in spinning, a long nerve-process {t.n), which has reached 

 the myotome and, curving along its outer margin, is passing onwards 

 closely under the epiblast. Fig. 12 is really a combination of ap- 

 pearances seen in different sections, in that the conditions of the right 

 side of the figure are to be met with three sections in front of those 

 of the left side. The roof of the cord is here filled in or occupied 

 by five ganglion-cells (gl.c.c), on each side the lateral or outermost 

 one {sp. c) is engaged in spinning its fibre in the same way and 

 direction as in the preceding figure. A third ganglion-cell (sp. c^) 

 is only commencing to send out a nerve-process, while the remaining 

 two have no processes apparent in the sections. 



A few sections caudad the appearances depicted in Fig. 11 are 

 encountered. Four ganglion-cells are included in the section: of these 

 three present nothing calling for special remark, and the fourth {sp. c) 

 links on to, or remains in contact with, one of its centrally-lying 

 fellows, while also engaged in spinning out a process in each of two 

 directions. The one of these processes is directed over, and along, 

 the outer side of the myotome, the other is destined to keep the cell 

 in touch with the central ones. The condition here appears to re- 

 present an early stage of such figures as Figs. 31 and 46. 



Yet another figure. Fig. 10, shows no fully developed ganglion- 

 cells, but there are several pyriform cells projecting, with well-marked 

 processes, from the roof of the cord. These cells are undoubtedly 

 developing in the direction of becoming ganglionic, and one of them 

 (sp.c) has already made much progress towards this condition. It 

 has projected out a long process, as yet hardly to be described as a 

 nerve-fibre, which reaches into the tip of the myotome. 



In another of the figures of this series (Fig. 6), taken from a 



