2 EB. W. MacBRID#. 
“wheels” are few in number and confined to the lateral processes, 1-6 in each, 
whereas in our larva they are extremely numerous. Numerous “wheels” with 
13-16 spokes are described by Prof. Chun (2) in a peculiar Auricularia which he 
fished up at Orotava at the Canary Islands, and which has been named Auwricularia 
nudibranchiata by Dr. Mortensen (8). 
A few words upon the general anatomy of the Auricularia larva may not be 
out of place here. As all zoologists are aware, it possesses, hke other Echinoderm 
larvee, a thickened band of ciliated ectoderm as locomotor organ, and this band has 
the form of a folded loop, the longest axis of which is parallel to the long axis of 
the larva; in a word, the loop has two long parallel sides and shorter anterior and 
posterior cross-pieces connecting them. The anterior cross-piece is folded backwards, so 
as to form a frontal loop surrounding the forehead or ‘ frontal field,” whilst the 
posterior cross-piece is folded forwards so as to surround an “anal field” in which 
the anus opens. This loop may be termed the anal loop. The adjacent portions of the 
frontal and anal loops are termed by Dr. Mortensen ( Quersiiume ”), which we may 
translate as anterior and posterior “transverse bars.” The mouth is situated ina 
depression between the anterior and posterior bars termed the oral field. The ciliated 
band, in addition to the re-entrant frontal and anal loops, is produced into a number of 
“processes” which are homologous with the arms of the Echinopluteus and 
Ophiopluteus larve. Of these the pree-oral processes are developed from the 
sides of the frontal loop; and the post-oral processes from the sides of the 
anal loop. Where the frontal loop passes into the sides of the ciliated band, there 
are developed the antero-dorsal processes. From these same lateral portions of 
the hand are developed further back intermediate-dorsal and postero-dorsal 
processes. Finally, where the anal loop passes into the lateral portions of the band, 
we have the postero-lateral processes. These last, in the opinion of Johannes 
Miller, showed a resemblance to the human ear, whence the name “ Auricularia” 
was coined to designate the larva. 
We have seen that A. antarctica cannot be identified with the larva of Synapta 
digitata, since in the latter the “ wheels” are few in number and are confined to the 
processes (1-6 in each). But there are other differences scarcely less striking. In the 
larva of Synapta digitata the outline of the ciliated band is flowingly sinuous, none of the 
processes being very strongly marked, whereas in our larva the processes are marked off 
by deep re-entrant folds and show some secondary plications. Then the spot where the 
frontal loop passes into the lateral portions of the ciliated band is at the anterior pole 
in the larva of Synapta digitata, but in our larva it is displaced far back on to the 
dorsal surface. The oral field is comparatively broad in the larva of Synapta, but in 
our larva it is reduced to a narrow slit, the anterior transverse bar actually overlapping 
the posterior bar at the sides. On the other hand our larva resembles the Orotava 
larva not only in the great number and wide distribution of the “ wheels,” but in the 
displacement of the point of union of the lateral part of the ciliated band with the 
