G. A. DREW ON YOLDIA -LIMATULA, SAY. 11 



and morphologically ventral to it. Under favorable conditions, blood 

 corpuscles may be seen moving along this space when the appendage 

 is being extended. Other blood-spaces occur in the connective tissue 

 of the appendage, but they are much smaller arid anastomose freely. 



The epithelium lining the groove formed by the longitudinal folding 

 of the appendage is densely covered with cilia. 



The animal while feeding, Fig. 10, is usually slightly tipped 

 ventrally from the perpendicular, and frequently has about one-third 

 of its posterior end above the mud. While in this position, the palp- 

 appendages are thrust out of the shell and one, at least, bends over 

 and inserts its tip in the mud. The cilia lining its longitudinal groove 

 immediately begin to elevate the mud, which is rich in living organisms. 

 The stream of particles passing along the groove is large enough to be 

 distinguished at a distance of some feet. In this way foraminifers, 

 ostracods, and even small lamellibranchs, and gastropods, together 

 with the smaller forms and mud, are passed along the groove, finally 

 between the palps, and so 011 into the mouth. Thus we find that 

 Mitsukuri's surmise, 8 based on finding sand in the grooves of the palp- 

 appendages of preserved specimens, was right. The palp-appendages 

 are food collectors. 



GILLS. 

 FIGURES 3, 19 AND 20. 



Although the gills have been well treated by Mitsukuri, 8 Kellogg 5 

 and others, some additional facts, both on the structure and function of 

 these organs, seem to make it allowable to go over the already rather 

 familiar ground. 



Each gill, Fig. 3, g., consists of a double series of rather broad, flat 

 plates, placed laterally edge to edge, and antero-posteriorly with their 

 flat surfaces opposed. 



This double series of plates is suspended from the body wall by a 

 thin muscular membrane. Anteriorly the gills pass beneath the 

 overhanging digestive glands, on the under sides of which the plates 

 gradually become smaller and smaller, and finally fade away. The 

 extreme anterior ends are continued as ridges which seem to represent 

 continuations of the suspensory membranes rather than gill plates, and 

 point to the probable origin of the membranes as folds from the body 

 wall. Posteriorly the gills likewise become smaller, and are finally 



