188 KARL WILHELM GENTHE, 
The mantle and the disk. 
The lips of the mantle with their peculiar armature are shown 
in Fig. 7. They are separated to a small extent only on the ventral 
side. On the dorsal side they are thin coming to a long sharp 
edge. These dorsal edges and the anterior (cranial) circumference 
of the lips are beset with strong chitinous spines. The anterior 
(cranial) face is otherwise smooth (except in the most ventral region), 
while the lateral faces bear the fine scattered spines first mentioned 
and pictured by Darwix, The inner (medial) surface bears the 
peculiar S-shaped row of fine spines (mentioned and pictured by 
Darwin) which together look like a rasp (in Fig. 7 the beginning 
of one row is seen ats). Besides these there are a great many 
fine long hairs. 
A peculiar sculpture (Fig. 9) is found all over the first or oral 
cirri, the head, and the “palps”. Very fine it is, indeed, but it may 
well be that it forms a kind of grater against which certain particles 
that pass in through the lips of the mantle are rubbed and thus 
more finely divided. The S-shape of the above mentioned row of 
Spines may perhaps be accounted for in this way that when the 
head presses against the lips the tip of the hood-like projection will 
rub against the upper part of the S and the rest against the lower. 
The stiff bristles which are found in one row on each side of 
the head are not respiratory in function as was supposed by Hancock, 
but they certainly act as a weel (as mentioned first by AURIVILLIUS). 
They interlock with the hairs on the medial surface of the lips, as 
can be seen in sections, and thus form such a perfect strainer as 
one might wish. Moreover the hairs on these lips which point 
outward will by the incoming current be bent backward and caught 
by the fine projections of the above mentioned sculpture of the head 
and thus add to the efficiency of the strainer.. The outgoing current 
will loosen them again. 
The stiff bristles of the two lateral rows cannot be respiratory 
in function, because they are quite chitinous and have no blood 
lacunae. They contain a furrow (Fig. 10) so that their cross section 
forms an open ring. This furrow bends at the base and continues 
as a fine canal for some little distance in the cuticle (Fig. 11 0). 
Sooner or later the canal is lost sight of and seems to lead nowhere. 
The bristles are perhaps sensory organs, but I have failed to trace 
any protoplasmic connection through the cuticle into them nor in 
