242 MR. A. T. WATSON ON THE STRUCTURE 
cause the elastic sheath, stretched around them like a sphincter, 
to slip from their outer surface, and settle as a folded ring 
about the front edge of the “ thorax.” For a short distance the 
“thorax” is also visible through, and tightly invested by, the 
basal part of the membranous cone. The branchial crown (0.2., 
Pl. 23. figs. 1 & 2) now appears like a lovely red or golden 
flower, and, basking in the light, may for a time continue quietly 
to enjoy the water, which it sets in motion with its tentacular 
cilia. The expanded tentacles are dorsally widely separated by 
the cephalic crescent (c.l.) into two lateral groups, and just 
below the outer margin of the crescent a groove, bordered with 
cilia, is visible. 
The ventral division is less apparent, but is marked by the 
outermost tentacles of each group being, like sentinels, usually 
slightly advanced within the crown; and whilst the swollen 
tricuspid lobes (¢./. & /./.), with ciliated surfaces, occupy its base 
(PI). 23. fig. 2), the dorsal lobe gently rises and falls as though in 
the act of breathing. Butif the call of hunger claims attention, 
or a desire for work arises, all ischanged. The tentacles become 
lively, the boughs bend towards each other across the open 
crown, or perhaps throw themselves violently outwards; opposite 
twigs incline and meet, whilst the bilobed tips, like miniature 
fingers, twitch and move as though striving to grasp something. 
Then, as the water does not supply the need, the worm, in its 
tube, curves over on one side until the surface of the sand is 
reached, and that which is desired can be obtained. When the 
animal is thus seeking sand, or fine particles of shell, these at 
once adhere slightly to the mucus of the bilobed tips of the 
tentacles, or are grasped by them and worked into the horseshoe- 
shaped internal hollow, which, as a ciliated channel, conveys them 
to the base of the crown. When the sandy particle has in its 
progress reached the three lobes, one of two things happens: 
it may either be kept in motion for a short time by the surface- 
cilia, and then be rejected without apparently having fulfilled 
any purpose whatever (the two ventral tentacles usually acting 
as “‘ejectors”), or, conveyed within the grasp of the lobes, it 
may be carried down, by a kind of peristaltic action, through 
the opening into the vestibule beneath. Powerful transmitted 
light is required to observe what follows, and in this way, with 
the aid of a suitable arrangement of the microscope and a low 
power, the fragment can be seen to be now revolving with a jerky 
