228 AMPHITRITE. 
which my attention was not specially directed while prosecuting the 
history of the Amphitrite.* 
But it has proved embarrassing to understand the contraction, and 
sudden reception, of many ciliated hydra within such narrow dwellings 
as they occupy, and their subsequent enlargement, unless by presuming 
their tubular conformation. At the same time, it is not to be readily 
comprehended how and where the liquid contents are discharged. 
Other partial mutilations are consequent on disease, or on violence. 
The tube of a specimen with a plume of fifty branchixe, expanding above 
fifteen lines, was shortened on the 3d of November. The occupant, now 
fixed anew at a point distant six diameters of the tube from the lower 
end, becoming very bold, even sustaining shocks without retreat. But 
in three weeks it lurked chiefly within, and the branchiz appeared to be 
diseased when shewing itself. ‘Towards the close of November, a quan- 
tity of mucilaginous matter was discharged from the orifice, and in some 
days the animal, rising from below, exhibited the bare ribs of the 
branchize only. Thus the cilia, consumed by disease, had been probably 
cast forth with other matter, or as: mucilage. Now shutting itself up in 
pertinacious retreat, I found two-thirds of the cilia regenerated on the 
13th of December, and the vigour of the plume seemed completely re- 
stored. Contrary to the original boldness distinguishing this specimen, 
it continued always reluctant to display itself during five months of sub- 
sequent observation. 
The practical naturalist cannot but be embarrassed at missing cer- 
tain characteristics assigned to this genus in the Systema Nature. The 
reason is explained by the preceding facts. 
As already said, the number of branchiz is constantly augmenting 
with the age of the specimen ; recollecting that those composing the 
* Viviani, Phosphorentia Maris, p. 14, 17, tab. iv., v.: Genuz, 1805, in 4to. The 
observations of this author on the anatomical structure of the Amphitrite ventilabrum merit 
notice. He seems disposed to render his specimen the type of anew genus, “ Spinographis, 
id est penicillus in spinam depictus.” But he cannot have remarked that ‘the spinal ar- 
rangement of the external parts is only accidental, resulting from disease. 
