NOTES AND QUERIES. 319 



was the remains of the Nereis. These facts seem worthy of record 

 because the meaning of the association between the worm and the 

 Hermit-Crab is only partly understood ; indeed, the whole subject of 

 the association of Eupagurus bemhardus, Sagartia parasitica, and 

 Nereis fucata stands in need of fresh and intensive study. — H. N. 



MlLLIGAN. 



ASTEEOIDEA. 



Rate of Locomotion in Sun-Stars. — The usual rate of locomotion 

 of the common Sun-Star (Solaster papposus) is not high. In a note 

 published in the ' Zoologist' of 1915 (pp. 437-438), it was remarked 

 that the average in a Sun-Star of 2 inches in diameter waa 1 inch in 

 26-1 seconds ; and subsequent observations have shown this to be 

 approximately the rate of locomotion of other examples of about the 

 same size. When occasion arises, however, a Sun-Star can travel 

 at a much greater speed. Several of the captive Sun- Stars observed 

 by me have had a peculiar habit (most marked in animals new to the 

 aquarium) of moving upon food (say a piece of fresh Sea-Urchin, 

 Crab, Shrimp, or Fish) placed close to them, then partially assuming 

 the usual feeding attitude, and finally quitting the food very suddenly 

 and retreating at a speed which I have not seen them attain under 

 any other circumstances. (I do not know the cause of this be- 

 haviour.) I determined to ascertain as exactly as possible the speed 

 of a Sun-Star when thus retreating, and I was able to do this in the 

 case of an individual of 2| inches in diameter. The Sun-Star (which 

 had been in the aquarium for ten days) retreated from a piece of 

 recently-killed Sea-Urchin, and three separate records were secured 

 in its succeeding wild career in the tank. It travelled in a horizontal 

 direction upon the rough vertical rockwork which forms the back of 

 the tank for a distance of approximately 10 inches in 30 seconds ; 

 it moved across the fine gravel on the floor of the tank for 

 7 inches in 30 seconds, and it climbed up the glass front of the 

 aquarium for 3f inches in 30 seconds. It will be noticed that the 

 Sun-Star was a small one. Large examples, say of 6 or 8 inches in 

 diameter, seem always to creep very slowly, at all events in an 

 aquarium. — H. N. Milligan. 



