232 MR. A. T. WATSON ON THE STRUCTURE 
means of a network of muscular fibres, can be opened or tightly 
closed at will (c.p., Pl. 24. fig. 8). Free communication can be 
thus established between the coelomic fluid-containing cavity 
and the surrounding sea-water. The ventral separation of the 
branchial processes is, doubtless, a development of what ap- 
peared originally as a “‘ notch” in the funnel-shaped lip. 
It is interesting to note that one member of this family, 
Myriochele (Mgrn. 4. p. 211, and 13. p. 410) is distinguished by 
the absence of cephalic branchie, development of these organs 
having apparently been checked at an early stage. 
During life the interior of the base of the crown is occupied 
by three lobes (Pl. 28. fig. 2), namely, the dorsal (c.l.), already 
mentioned, and two lateral ones (J./.) formed by swellings at the 
base of the ventro-lateral branchial processes, which, distended 
by the ccelomic fluid, and meeting in the centre, may form more 
or less completely a kind of vestibule—an arrangement which 
appears to have hitherto escaped notice. Beneath these lobes, 
which almost disappear owing to contraction in preserved speci- 
mens, is the mouth (m., Pl. 23. figs. 1 & 3), a transverse opening 
situate a little distance from the inner dorsal surfaces, the space 
between the mouth and the ventral boundary being occupied 
by the peculiar “‘ Lippen-organ” (J.0., figs. 1,3 & 7), with its 
massive bilobed lips, first figured by von Drasche (12. p. 6, 
pls. 1. & i1.), the funetions of which will be hereafter described. 
The branchial crown is marked off from the “ thoracic” region 
by a reddish-brown fold, which commences laterally and becomes 
very prominent dorsally (c., Pl. 24. figs. 7 & 8). 
There is a single black or dark-coloured ‘“‘eye-spot”’ on the 
ventral face of the crown (e., Pl. 25. fig. 20), situate at the base 
of the branchiz on either side of the opening. 
The segments are neither divided by distinct constrictions, as 
in Arenicoia and Clymene, nor are they sharply divided from 
each other; only here and there does the body contour show a 
slight incurving, indicative of their demarcation (Pl. 25. fig. 20). 
The “ thoracic region” comprises the buccal segment and three 
other short segments fused together, the only external indica- 
tions of which are three bundles of simple yellow, slightly 
pinnate bristles. Of these, the first two ouly are visible in the 
ventral view (Pl. 25. fig. 20); as the third bundle, consisting 
of much shorter and less numerous bristles, is situate quite 
dorsally. Internally there is a septum between the buccal 
