14 THE VOYAGE OF H.M.S. CHALLENGER. 



with a yellowish-brown coloured mass of a fatty nature. Between the two walls of 

 the stomach, nuclei of nearly the same size as those of the connective tissue are visible. 



Nervous System. — The supracesophageal ganglion, also, has nearly kept its original 

 position; it is situated againsl the oesophagus, a little anteriorly to the place where it 

 communicates with the stomach. In PL I. fig. 2 it is figured in its natural position 

 ami condition; in PL III. fig. 5, and PI. I. fig. 4, it is seen in transverse section; 

 numerous rounded ganglionic cells are placed at the periphery, and the whole interior of 

 the ganglion is occupied by the medulla. PI. I. fig. 4 distinctly shows the commissures 

 which serve to unite the ganglion with the large thoracic ganglion. In the preparation 

 which is figured (PI. I. fig. 2) these commissures could not be made out, nor has this been 

 possible in 'any of the other preparations I made by the aid of needles. 



This thoracic ganglion represents alone the whole ventral nerve-cord ; together with 

 the thorax, it has changed its place and has been transposed in a direction towards the 

 front of the animal, so as to be now attached before the supracesophageal ganglion; it 

 has an elongate oval shape with numerous ganglionic cells at the periphery. In a trans- 

 verse section such as that figured (PI. I. fig. 5), we observe that the ganglionic cells form 

 a much thicker layer on the side which is directed towards the thorax than on the other 

 side ; the lateral symmetry of the ganglion is very distinct, the medulla forming two 

 rounded portions which meet in a straight line in the middle of the ganglion. The nerves 

 given off from this ganglion as well as those from the supracesophageal ganglion are 

 extremely delicate and are hardly recognisable as such; two somewhat stronger nerves 

 start from the commissures very close to the supracesophageal ganglion, and a distinct 

 nerve is attached terminally to the thoracic ganglion, but as for other nerves, I 

 found it impossible to distinguish them with certainty from the fibres of the connective 



tissue. 



There are no organs of sense ; even the sense of touch can be only very slightly 

 developed, as the whole body is enclosed within a chitinous bag bearing only chitinous 

 spines on its surface. The hairs on the antennae (PI. I. fig. 3) no doubt once per- 

 formed the function of organs of touch, but after the antenna has attached itself the 

 function of these hairs can no longer be of any importance. Close to the supra- 

 cesophageal ganglion I always observed two little bodies, which, from their position, I at 

 first felt inclined to consider as belonging to the nervous system. They are kept in 

 their places by the connective tissue, and they are situated near the corner between the 

 stomach and the supraoesophageal ganglion. Their structure is that of an oval bag 

 slightly pointed at one or both extremities, lined by an extremely delicate mem- 

 brane and filled with a granular substance of a brownish-yellow colour, having 

 numerous nuclei scattered throughout its interior (PI. I. fig. 2, gh). Most probably 

 these organs represent the remains of the appendages of the oesophagus (PI. II. 

 figs. 1, 2, G) of the pedunculated Cinipedia, which are very distinctly developed in the 



