AMPHITRITE. 237 
figs. 3, 4, 5. Besides corresponding coloured spots, several pair of pecu- 
har shaped, flattened, transparent organs, endowed with some extension 
and contraction, and apparently of the same consistence as the cilia, pro- 
ject from the back of the rib.—Fig. 6, a, 6, c, stem enlarged. Two stout 
pointed antennular spines are situate in the centre of the bottom of the 
plume or funnel, where the converging branchiz meet below. These 
organs are susceptible of prolongation, and have the faculty of transmit- 
ting particles up the back.—Fig. 7, enlarged. 
The plume is proportionally larger and more luxuriant than that of 
the Amphitrite ventilabrum. It is finely variegated with different shades 
of brown and yellow. Orpiment orange is the colour which predominates 
on the body. 
This animal dwells in a tube surpassing its own length, which is not 
of mechanical construction, but is formed by a spontaneous exudation 
from its whole body, comprehending the extremities, or from any part 
of it. When originally produced, it is clear as crystal, completely ex- 
posing the tenant’s external organization, of corresponding figure. If de- 
prived of the surrounding element, its aspect is somewhat gelatinous, but 
it seems truly of silken fabric, and becomes quite opaque with age. The 
upper part is corrugated, darker, thicker, and stronger than the rest, evi- 
dently for protection of the plume, which is the most delicate part of the 
creature. The lower extremity is close and obtuse.—Plate XXXII.’ 
fisnAe 
The secretion whence the tube is derived, must be accounted very 
copious, as several tubes can be formed in succession. Whether any 
share of it is afforded by the plume seems uncertain, farther than as a 
glutinous matter, overspreading the vicinity, as a preservation of the 
animal parts from abrasion. 
Contrary to the direction of the tube essential for discharging the 
mechanical functions of the Amphitrite ventilabrum, naturally vertical, 
that of the Amphitrite bombyx is usually horizontal. Herein the plume 
is stationary, it has no such functions to discharge ; nor, although the 
tube be occasionally vertical, and the plume remains free, is there any 
revolution, as by the former species. It affixes readily to all substances. 
