4/2 DEVELOPMENT OF ELASMOBRANCH FISHES. 



inserted, but fills up the whole space within the outline of the 

 body. At one point a nerve (;/) is seen to enter. In connection 

 with this are a number of ganglion cells, the exact distribution 

 of which has been reproduced. They are scattered irregularly 

 throughout the suprarenal body, but are more concentrated at 

 the smaller than at the large end. It is this small end which, 

 in succeeding sections, is entirely replaced by a sympathetic 

 ganglion. Wavy fibres (which I take to be nervous) are dis- 

 tributed through the suprarenal body in a manner which, roughly 

 speaking, is proportional to the number of ganglion cells. At 

 the large end of the body, where there are few nerve cells, the 

 typical suprarenal structure is more or less retained. Where 

 the nerve fibres are more numerous at the small end of the 

 section, they give to the tissue a somewhat peculiar appearance, 

 though the individual suprarenal cells retain their normal struc- 

 ture. In a section of this kind the ganglion and nerves are 

 clearly so intimately united with the suprarenal body as not to 

 be separable from it. 



The question naturally arises as to whether there are cells of 

 an intermediate character between the ganglion cells and the 

 cells of the suprarenal body. I have not clearly detected any 

 such, but my observations are of too limited a character to settle 

 the point in an adverse sense. 



The embryological part of my researches on these bodies is 

 in reality an investigation of later development of the sym- 

 pathetic ganglia. The earliest stages in the development of 

 these have already been given 1 , and I take them up here as they 

 appear during stage L, and shall confine my description to the 

 changes they undergo in the anterior part of the trunk. They 

 form during stage L irregular masses of cells with very con- 

 spicuous branches connecting them with the spinal nerves (PI. 

 18, fig. 3). There may be noticed at intervals solid rods of cells 

 passing from the bodies to the aorta, PL 18, fig. 2. These rods 

 are the rudiments of the aortic branches to which the suprarenal 

 bodies are eventually attached. 



In a stage between M and N the trunks connecting these 

 bodies with the spinal nerves are much smaller and less easy to 

 see than during stage L. In some cases moreover the nerves 



1 Antea, pp. 394396. 



