^OTKS AND QUERIES. 8l9 



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

 l)Ocause the moaning of tho association hotwoon tho worm and the 

 Hermit-Crah is only partly understood ; indeed, the whole suhjcet of 

 tho association of Eujmyurus bemkardus, Sagartia parasitica, and 

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



MlLLKlAN. 



ASTEROIDEA. 



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

 of tho common Sun-Star {Solaster impposus) is not liigh. In a note 

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

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

 2G-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 mo 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 slowdy, at all events in an 

 aquarium. — H. N. Milligan. 



