460 



ually until at the end of a week's time there was a perfect meshwork 

 of burrows in view through the glass that had been kept darkened. 

 These passageways rarely descended more than 7 cm from the sur- 

 face. Sooner or later the outer openings of some of the burrows be- 

 came covered over with debris and some 1 purposely closed. They 

 were never reopened, the water of the burrow apparently containing 

 sufficient oxygen, nor did the animal so far as I know, ever appear 

 upon the surface. At the end of two weeks time some of the specimens 

 had died but the others were active and apparently in a normal condi- 

 tion; at all events the forward end of the alimentary canal in some of 

 the specimens that I have sectioned, contained food, undigested and 

 apparently only recently captured. 



The food of this species consists mainly of organic debris in which 

 it is possible to recognize bits of plants, numbers of what appear to 

 be vegetable spores and occasionally foraminifera, sponge spicules and 

 other substances of unknown origin. In some specimens sponge spic- 

 ules had made their way through the intestinal wall and were located 

 in various parts of the body, in one instance in the brain itself. Some 

 of the foraminifera, of the Rotalia type, had been taken in entire and 

 their protoplasmic substance was still in a fair state of preservation. 

 Many of the plant spores and other vegetable substances had likewise 

 escaped comminution by the radula. On the other hand there were 

 many pellets of organic matter, finely ground and apparently adhering 

 together by means of mucus, that may have been subjected to the 

 action of the radula, though it appears more probable that these sub- 

 stances had been collected by the lips and molded by them into a ball, 

 the large tooth of the radula serving merely to carry the bolus back 

 into the stomach-intestine. 



Along with some of the above mentioned species of Chaetoderma 

 were several specimens that undoubtedly must be considered as mem- 

 bers of Thiele's proposed genus, Prochaetoderma. They are invested 

 with a thin yet very rigid cuticle owing to the strongly developed 

 spicules and were accordingly very sluggish in their movements. A 

 few were placed on the surface of the mud in an aquarium and the 

 first specimen disappeared from view in two hours and nine minutes; 

 another in forty-one minutes more; while the others required from four 

 to nine hours. Their method of excavation was essentially the same 

 as in the foregoing species- chiefly by means of the prothorax assisted 

 by slight movements of the body proper. In some cases they formed a 

 relatively short tube of wide calibre communicating with the surface 

 by the small opening through which they entered. The majority, 

 however, formed tunnels immediately beneath the surface after the 



