History of a transient nervous apparatus in certain Ichthyopsida, 357 



nection with the central cell — a break which it has not seemed 

 fitting to fill in from the imagination. 



The figure shows three ganglion-cells (w. gl c) resting on the cells 

 of a spinal ganglion. In passing, it is interesting to remark how 

 frequently one meets with this phenomenon. Of the three cells the 

 largest one is turned towards the cord, and would have a connection, 

 in some form or other, by means of its nerve-process, with the axis- 

 cylinder of the cell lying in or on the cord. The two outer cells are 

 applied to the blunt end of the former cell, and one of them has a 

 nerve-process passing in the direction of the myotome. 



In the remaining figures (Figs. 42 and 43, plate 24) from the 

 series we again encounter cells in close topographical relationships 

 with cells of the spinal ganglia. Fig. 42 — a combination of what is 

 met with in two sections — furnishes a very curious drawing. There 

 are two transient ganglion-cells in the myotome (gl.c^)] of these one 

 lies at the apex, the other embedded in the outer epithelium of that 

 structure. Applied to the former of these cells is a ganglion-cell, 

 whose axis-cylinder process cannot be traced far, but in contact with 

 this cell in its turn a fourth ganglion-cell is seen with nerve-process 

 (n.p) passing into the top of the cord. 



The other figure on plate 24 (Fig. 43) resembles Figs. 31 and 35. 

 In it a large ganglion-cell (w.gl.c) rests on cells of the spinal gangKon. 

 It is bipolar, and its two nerve processes pass one in the direction 

 of the myotome, the other towards the spinal cord. In this instance 

 the axis-cylinder does not appear to pass right through the cell. The 

 other two figures from the series do not require description at this 

 stage; they will be dealt with in another connection. 



The centrally-lying ganglion - cells of the transient system, as 

 depicted in Fig. 42, are now provided with capsule-cells (c. c) in close 

 application to the ganglion-cells. 



The most striking features of the apparatus in this embryo are 

 1) the number of groups of ganglion-cells, often like those of Figs. 43 

 and 53 in some respects, lying in the mesoderm; 2) the frequent 

 position of such groups in the immediate neighbourhood of the spinal 

 ganglia; 3) the absence of any strongly pronounced development of 

 sub-epiblastic nerves, although, as already stated, such are not entirely 

 wanting; and 4) the number of nerves which are processes of single 

 ganglion-cells. 



From another embryo (No. 453) of the same size as the above, 

 — an embryo preserved in potassium bichromate and osmic acid, — 



24* 



