THE DONAX IN HIS HOME-BURROW. 159 



shell, where the "head" might be expected, you will notice, as you care- 

 fully dissect your donax, that there are two little pointed knobs protrud- 

 ing from under the mantle. V 



I knew what these were, as well as I knew the use of the " foot," but 

 I was astonished to see how much there was of both of them when I had 

 put my captives into the basin. Out from the sharp end of each little 

 wedge slid a thin, flexible, three-cornered bit of flesh, like a knife-blade, 

 with crinkled, waving edges, the point of which was thrust into the sand, 

 twisted a trifle to catch hold, and then suddenly contracted, drawing the 

 mollnsk down until the point of his shell was out of sight. Eepeating 

 the operation far more rapidly than I can write about it, he made his way, 

 foot-first, straight down into the sand as fast as he could have walked 

 across it — faster, indeed, for he cannot walk at all except by burying the 

 edge of his top-heavy armor deep enough in the earth to maintain an up- 

 right attitude. It was entertaining to see how, in my crowded aquarium, a 

 little fellow would stretch his flexible spade until it was longer and broader 

 than his whole shell, and how he would feel about with the sharp, mus- 

 cular tip, stirring up the sand until he struck an easy place to enter; or, 

 witli its aid, would creep awkwardly about among his companions, who 

 always took his rough elbowing good-naturedly. 



But the donax cares to go only deep enough in the sand to be well 

 hidden while he is feeding. Sinking down backward, he thrusts up 

 through the opened blunt end of his shell the knobs which we noticed 

 there in our dissection, now stretched forth into two pipes, with which 

 he can reach out to a distance almost twice the length of his shell. 

 Through one of these pipes he sucks in a constant stream of sea-water, 

 which bears him his minute food; and through the other pipe is carried 

 away the waste water after his stomach has taken up all the food that it 

 brought. 



Very pretty was it to lean close over that basin of water and see those 

 dozens of pairs of slender tubes, of all lengths, from nothing, hardly, to 

 an inch and a half, looking almost as white and clear as if made of glass 

 — and far more lovely — elongating and retracting, waving about with 

 slow, graceful motions, or gently nodding together as if they enjoyed 

 each other's society. And the more closely one observed the white, silky 

 tubes, the more beautiful they appeared. Each lower tube bears at its' 

 end a crown or fringe which resembles the frost-leaves on a window-pane 

 as much as anything I can think of, or it is like a circle of snowy spruce- 

 boughs all pointing inward. 



This little fringe is very easily moved by means of the gossamer 



