114 Papers from the Department of Marine Biology. 



at the bottom. Fishes, often of large size, always swam towards them, 

 but when within a few inches turned and swam away. Either by 

 sight, or some other sense, perhaps stimulated by some exhalation from 

 the comatulids, these animals were recognized as inedible. 



FOOD AND FEEDING. 



Examination of the contents of the stomachs of living crinoids were 

 made on two different occasions. One day two crinoids, which had 

 been in the live-car for several days, were brought to the laboratory 

 and the contents of their stomachs were carefully examined under the 

 microscope. No essential difference between the two specimens was 

 noted. In each case, the greater part of the food material was green 

 algae, chiefly unicellular, but some linear forms (thread-alga?) were also 

 noted; a few diatoms were detected and some foraminifera; in one of 

 the stomachs, several radiolarians were also seen. There was no indi- 

 cation that other than living food material had been taken into the 

 stomach. All of the material was virtually undigested. On another 

 day a study was made of the contents of the stomachs of two crinoids 

 just brought into the laboratory from the reef. In both individuals 

 the food material was identical with that of the crinoids which had 

 been living in the live-car. In one specimen a piece of a red alga was 

 noted and in the other some fragments of minute Crustacea. These last 

 were the only particles of animal food noted and were the only things 

 observed that could possibly have been taken in as dead plankton. 

 It was made perfectly clear that the comatulids at Maer, at least in the 

 dry season, are all vegetable feeders, and that the percentage of animal 

 food is negligible. But it is possible, of course, that during the rainy 

 season there may be a change in the composition of their diet ; on that 

 point there is no evidence to offer. 



It is not easy to determine beyond question the manner in which 

 the food reaches the stomach. It is easy to suppose that the food is 

 simply swept into the mouth by the current of water flowing along 

 the ciliated furrows of the arms and disk, but I did not succeed in 

 demonstrating such a movement, although there is no reason for 

 doubting its reality. The multibrachiate forms keep the arms more 

 or less widely spread out when they are at rest, but in the ten-armed 

 species they are often more or less erect and sometimes quite rigid. 

 In the aquaria and live-car the arms are frequently if not constantly 

 curving in towards the mouth and the tips sweep the surface of the 

 disk lightly. Individuals living on the lower surface of rock-fragments, 

 since they are attached by the aboral side, rest with the ciliated grooves 

 and mouth downward, away from the surface of the rock. It is 

 therefore evident that, unlike starfishes and echini found in similar 

 situations, they get their food from the water directly and not from 

 the surface on which they rest. Taking all the facts observed with 

 reference to the nature of the food, the position and movements of 



