6 VERRILL 



about six hours, while the tide was above the outlet of the pool, 

 which was on a nearly smooth, gently sloping, granite ledge. 



In brief, nearly all left the pool, and travelled downward, but in 

 irregularly divergent lines, to various distances, varying from one 

 to about fifteen feet. The majority followed a nearly straight 

 course down the more sloping parts of the ledge, but were readily 

 diverted to one side or the other by small variations in the slope. 

 Those that travelled the greater distances probably left the pool 

 soonest, and were perhaps in more active condition. Selecting a 

 dozen or so of the best travellers, they might average ten feet to 

 twelve feet in six hours, or nearly two feet an hour, providing they 

 left the pool about as soon as it was covered by the tide, which was 

 probably true of some of them, at least. As their motions are 

 rather deliberate and continuous, they could, no doubt, keep up this 

 rate for many hours, or about 336 feet in a week. 



Yet these were mostly rather small, from 4 to 6 inches across, and 

 the larger ones were found to travel much faster than the young 

 ones, for they have a much larger number of sucker-feet, which are 

 also stronger and longer. 



Such observations as the above give, of course, only an approxi- 

 mate idea of their rate of travel. These were neither impelled by 

 hunger nor by cold, but merely by an instinctive tendency to seek a 

 lower level. A stronger stimulus might have increased the speed. 



Very large starfishes, like many of the west coast species, would 

 probably travel very much faster, and perhaps those with many rays 

 and a vast number of suckers, like Pycnopodia and Solaster, would 

 be still more speedy. By actual count a half-grown Pycnopodia was 

 found by the writer to have over 22,000 ambulacral feet. 



At any rate, the observed speed would be quite sufficient to permit 

 them to ascend or descend a sloping sea bottom quickly enough to 

 avoid any ordinary changes in the temperature of the water liable to 

 be injurious, and also sufficient to enable them to seek their ordinary 

 food on new grounds. It is known that, in spite of their voracity, 

 they can go for many days, or even weeks, without any food and still 

 remain active and in good health. 



However, there are other families of starfishes that are far more 

 lively, while some others are far more sluggish. 



The most lively starfishes known to me belong to the genus 

 Luidia. Some of these are very large species. 



These live on bottoms of fine sand or mud, more commonly in 

 rather deep water, but often close to the shore in sheltered, shallow, 



