694 JAMES L. KELLOGG 
of a few of the plates at the extreme anterior ends of the gills, 
which are sometimes much distorted and swollen |italics mine], 
all of the plates are alike in shape and structure.” 
The modified plates which Drew saw are always present, are 
two in number (the third and fourth in the series, though if 
this may possibly vary, such variation has not been seen) and 
are always found only on that side of the gill nearest the median 
plane of the body. They are modified to dispose of gill collections 
which are not to be sent to the palps, being one more of the several 
anatomical structures that are developed to aid the ciliary 
mechanisms. Figure 68 represents the anterior end of the right 
gill seen from the inner side, so as to show the modified plates 
(mp). Along the sides of the plates is the series of ciliated 
unions (cu) that I have described elsewhere. On the ventral 
surface of the gill, and between the two series of plates, is a 
broad ciliated canal (vcc). The edges of the plates above cu 
are not ciliated, but below this line is a full ciliation of the plate 
edges which drives water upward between them (see the long 
feathered arrow) into the epibranchial space, and carries particles 
brought to them very swiftly down to the ventral canal. Here 
the collections are carried forward, but are halted momentarily 
about opposite the fifteenth plate by a narrow, backwardly 
directed tract lying along the bases of the inner plates (see also 
fig. 69, a ventral view). Very small amounts seem to pass this 
point without interference. It is possible that the halt is made 
here in order to facilitate the transfer of material to the palps, 
the oral groove of which, at times, lies against this region of the 
gill. At any rate, if this transfer is not made, the material, 
after revolving a few times, continues on toward the modified 
plates. These, like all parts of gills and palps, as described by 
Drew and myself, are capable of extensive movements. They 
are never in close contact (they possess no ciliated disks on their 
apposed faces) but may spread wide apart. Their apposed 
faces are richly ciliated, and material brought by the ventral 
canal is seized and quickly forced through between them into 
the epibranchial space. Here, on the wall of the suspending 
membrane (gm), and aided, perhaps, by the outgoing stream of 
