228 AMPH1TRITE. 



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 hydrae 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 branchiae, 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 branchiae 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 

 branchiae 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 branchiae is constantly augmenting 

 with the age of the specimen ; recollecting that those composing the 



* Viviani, Phosphorentia Maris, p. 14, 17, tab. iv., v. : Genuse, 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 a new 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. 



