66 Royal Society, 



rested upon their antennae on reaching the bottom, and paddled 

 themselves about by their fore-limbs and tail. 



The author remarks that in all their movements the males exhibit 

 a tendency to turn towards the left side, and concludes the rationale 

 of this fact to be, that the brain on the right side being more deve- 

 loped at the part from which the right antenna derives its nerves, a 

 corresponding predominance is given to the power of the locomotive 

 organs on that side. 



When fully developed, each antenna in both sexes consists of 

 twenty-five segments. Of these, the first thirteen present nothing 

 remarkable ; but all the remaining pieces on the right side enter 

 into the composition of the curious prehensile organ which forms 

 the principal subject of the paper. 



This organ is composed in the following manner: — The fourteenth 

 and four following segments are dilated into a large flask-like organ, 

 the neck of which is eked out by the nineteenth and twentieth. 

 The next two segments are fused together, and are articulated with 

 the foregoing by a simple joint, and the whole of the remaining 

 segments form another piece similarly articulated with the inter- 

 mediate piece; so that the whole results in two simple joints sus- 

 ceptible of flexion in one direction only. On the eighteenth segment 

 is a barbed process having its apex directed backwards, and its an- 

 terior border beset with sharp teeth. Two processes of the same 

 nature, but differently placed and more elongated, lie side by side 

 upon the fore-part of the first compound segment. This piece and 

 that which succeeds it act upon each other like a pair of jaws, each 

 furnished with an array of sharp conical teeth, while the last com- 

 pound member of the series plays over the upper surface of the 

 eighteenth segment. 



The author then proceeds to describe the muscles which move 

 this complex apparatus. The extensors are small and feeble, but 

 the flexors are, as might be anticipated, more complex and power- 

 ful. They are two in number. The first has its origin in the large 

 flask-like dilatation, and is inserted by a tendon into the second 

 compound piece, from which the second muscle arises, and is in- 

 serted, also by tendon, into the third piece. 



April 14. — A paper was read, entitled "On certain Functions of 

 the Spinal Chord." By J. Lockhart Clark, Esq. 



These investigations were undertaken by the author partly with 

 the view of settling the long- agitated question whether all the roots 

 of the spinal nerves terminate in the spinal chord, or whether any 

 part of them ascend within the white or grey columns to the brain. 

 The preparations employed for this purpose were made according to 

 the new method described in the author's former communication, 

 Phil. Trans. 1851, Part 2; and the animals selected were the Ox, 

 Calf, Cat, Rat, Mouse and Frog. Of the spinal chord of the Cat, 

 he has succeeded, after much trouble, in rendering transparent 

 longitudinal sections -Jyth of an inch in thickness, and more than 

 two inches in length, including the roots of four or five pairs of 

 nerves. 



