380 W. J. CROZIER 



tract of the large Stichopus moebii Semper, which is so abundant 

 on grass-free bottoms of sandy mud about the Bermuda Islands. 



An adequate estimate of this nature requires information upon 

 the following points : 1) the maximum amount of material usually 

 contained in the gut of Stichopus of different sizes; 2) the fre- 

 quenc3^ with which holothurians of different sizes feed; 3) the 

 frequency-distribution of sizes in the Stichopus population; 4) 

 the actual numerical abundance of Stichopus in regions of known 

 area. 



It is necessary to explain, in connection with 1) and 2), that 

 Stichopus is very convenient for a study of this kind, since as a 

 rule the intestine is filled, completely, before defecation is begun ; 

 and that an appreciable interval elapses between defecation and 

 subsequent feeding, so that the gut is for a time entirely, or almost 

 entirely, empty of solid contents. Feeding may begin before the 

 intestine has been emptied completely, but each filling of the gut 

 seems to be handled as a unit ; characteristically, the whole con- 

 tents of the intestine are voided rather rapidly and in a con- 

 tinuous mass. Hence the long castings which are to be seen upon 

 the bottoms where Stichopus lives. 



These observations were confined to shallow-water situations, 

 and the 'quantitative" data refer to a season (September-Novem- 

 ber, 1917) when the temperature of the water was between 17° 

 and 24°C., usually below 20°C. Stichopus occurs down to 

 depths of 8 fathoms, and possibly more. It is almost certainly 

 more abundant, however, in shallow water along the shore. 

 ' II. 1. The amount of sand held in the intestine of Stichopus 

 just before evacuation is begun appears to be somewhat variable, 

 in animals of about the same size, even when they are collected 

 in the same locality. Large numbers of them were opened, at 

 various hours of the day and at different stages of the tide, and 

 from the examination of the alimentary tracts of these individuals 

 thirty-nine were selected which seemed to be filled to the maximal 

 extent. The gut contents, in each of these cases, were removed 

 to a finger bowl, well washed with rain water, the sand filtered 

 off, dried in the sun, and weighed. All of these animals were 

 obtained upon one kind of bottom, hear Agar's Island. Figure 1, 



