3l4 G[LMAN A. DREW. 



somewhat nearer the shore^ and they may be very numerous 

 at considerable distances from places where Yoldia is known 

 to thrive. 



In picturing the conditions under which these animals live 

 along the coast of Maine, the reader should not fail to take 

 into account the average tide of about ten feet, which keeps 

 the water very pure over a comparatively foul bottom. The 

 fauna and flora of these bottoms are very abundant and di- 

 versified, but have not been carefully catalogued. Diatoms 

 of several species abound, and form a large part of the food 

 of Nucula. Other Algee, Ostracods, Foraminifers, small 

 Lamellibrauchs, and Gastropods are also very abundant, and 

 small individuals of most of these forms are occasionally 

 found in the stomachs of preserved specimens. 



While I have never succeeded in getting individuals to 

 form brood-sacs in captivity, they live well in aquaria, and 

 may be kept for several weeks either in vessels containing 

 the mud in which they normally live, or in vessels without 

 this mud. It is not even essential that the water be changed 

 very frequently. 



When placed in vessels containing mud they bury them- 

 selves, and seem never to come to the surface to stay for any 

 considerable time. They are at all times comparatively 

 sluggish, and seem to wander around in the mud by slow 

 thrusts and retractions of the foot, which is a very perfect 

 burrowing organ. When placed in mud that is just suffi- 

 ciently deep to cover them, their movements can be followed 

 fairly well by the movements of the mud. To see them 

 feeding it is necessary to use only a very thin layer of mud. 

 The action of the palp appendages can then be observed. 

 They perform the same function that is performed by similar 

 appendages on the palps of Yoldia (1), that is, they are 

 food collectors. Nucula delphinodonta seems normally 

 to feed beneath the surface of the mud, so feeding cannot be 

 observed as easily as it can be in the case of Yoldia (Text- 

 fig. T). 



The movements of the foot are best observed by placing 



