660 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



one individual, and putting it in a large disli whicli was filled with 

 sea-water, he found that he could at pleasure lead the starfish in any 

 direction by holding a morsel of crab an inch or two from the end of 

 one of its rays, and continuously withdrawing the food as the starfish 

 approached it. Moreover, he could at any time reverse the direction 

 of advance by transferring the food to the opposite side of the animal, 

 and holding it for a short time near the tip of a ray. Thus he could 

 entertain no doubt that starfish have a well-developed sense of 

 smell. 



With the view of ascertaining whether or not this sense is localized 

 in tbe ocelli, he removed the latter fi'om all the rays of the same star- 

 fish, and then repeated the experiment. The result was the same, thus 

 showing that the ocelli are not specially concerned in the sense of 

 smell. Nor was there any change produced when the rays were pro- 

 gressively truncated further and further down : the olfactory sense 

 was found to be distributed throughout their length, and as the author 

 considers, as the result of other experiments, over the lower surface, 

 while not extending to the upper surface. 



Confirmation is also given to the view that one function of the 

 pedicellarise, at all events, is that of assisting locomotion by seizing 

 fronds of seaweed, to hold them steady until the pedicels have time to 

 gain attachment by their adhesive disks. 



When an Echinus is inverted on a flat surface under water, so that 

 it rests upon its aboral pole, it will quickly right itself by using two 

 or more adjacent rows of pedicels ; and in his earlier paper the author 

 discussed the question whether the execution of such a manoeuvre was 

 to be considered due to the co-ordinating influence of a nerve-centre 

 having a dim sense of gravity, and feeling, as it were, this sense dis- 

 turbed by the unusual position in which the animal is placed ; or 

 whether the manceuvre was to be considered due merely to the serial 

 action of the pedicels themselves, sundry experiments tending to show 

 that the manoeuvre must at least in part be due to the co-ordinating 

 influence of a nerve-centre. Mr. F. Darwin, having read the account 

 of these experiments, suggested an additional one, which Dr. Romanes 

 has tried, with the result of definitely settling the question. This 

 experiment and its results are as follows : — 



An Echinus is inverted with its aboral pole resting on the bottom 

 of a large bottle filled to the brim with sea-water. The mouth of the 

 bottle is then corked (no air-bubbles being included), and jjlaced ujjon 

 the rotating aj^paratus which Mr. Darwin and his father used for in- 

 vestigating the geometrism of plants, so that the Echinus was conti- 

 nuously rotated in a vertical plane. So long as the rotation was 

 continued, whether rapid or slow, the Echinus did not attempt to right 

 itself ; but, when the rotation was allowed to cease, it began to do so 

 after two or three minutes. Moreover, if allowed to do so until it had 

 raised itself into the equatorial, or any other intermediate position, 

 and the rotation were then resumed, the position gained was perma- 

 nently retained so long as the rotation was continued. Therefore no 

 doubt could be entertained that the effect of the rotation was that of 

 confusing, as it were, the co-ordinating influence of a nerve-centre. 



