2J4 EDWARD S. MORSE. 



gill plates, and in this position are in gentle and constant motion 

 with occasional side jerks. After watching these browsing 

 movements for awhile one becomes convinced that the behavior 

 of the ends of the palpi is that of feeding. Even the peculiar 

 jerks at times suggest that some larger morsel has been caught. 

 The protean shapes the appendage assumes are shown in Fig. 16. 

 The strong ciliary action of the gills is continually sweeping along 

 particles of organic matter toward the feeding appendages which 

 gather the stuff and convey it by ciliary action to the mouth. 

 The movements of these appendages may be distinctly seen 

 through the ventral membrane and at no time are 

 they at rest. The continual ingestion of food is in- 

 dicated by the great quantity of excreta which is 

 voided. In this connection it is interesting to 

 note that Drew 6 in his memoir on the life habits 

 of Yoldia limatula, another member of the Proto- 

 branchia, describes long appendages to the palpi 

 which extend backward beyond the posterior end 

 of the shell and rest on the sand. These appendages 

 are semi-tubular and being ciliated "rapidly elevate the mud 

 which is full of living organisms and finally pass it between the 

 palpi," and thence, of course, to the mouth. 



Mitsukuri, having described the palpi in Nucula proximo,, 

 says: "At their posterior end there are two remarkable struc- 

 tures. One of these is a hood-like structure which is the posterior 

 prolongation of the united upper edges of the inner and outer 

 palpi. The other, lying immediately below the first, is a long 

 tentacular appendage. It is a hollow tube, open, however, 

 along a line on its posterior aspect, and having its cavity con- 

 tinuous with the space between the two palpi. As it has been 

 seen protruded with the foot outside of the shell, and since, in 

 alcoholic specimens, a great deal of dirt and sand is found along 

 its length and between the palpi from its base to the mouth, it is 

 no doubt a food-procuring organ, probably sending a constant 

 stream of nutritive matter to the mouth by means of its cilia. 

 It is interesting to notice in connection with this appendage that 

 in Nucula, the gills, unlike those of ordinary lamellibranchs, 

 must be practically useless for obtaining food, as will be evident 



