AMPHITRITE. 229 
plume have been seen from six to ninety-two. Their accession may be 
observed with greater convenience from their first appearance as flexible 
hairs, on the edge of the fans next the trowels, where several are gene- 
rally discovered in progress. After advancing considerably, these, the 
ribs, still remain bare, the cilia being generated last. Among the nu- 
merous figures embellishing Miiller’s celebrated work on Danish Zoology, 
is the “ Amphitrite penicillus” (ventilabrum], which he distinguishes by 
“ tentaculis binis setaceis ;’* and other authors assign no feathered approwi- 
mate feelers to the genus. As entering its definition in the Systema Na- 
ture, 1am unwilling to affirm that Miiller, to whom science owes such deep 
obligations, is wrong ; but most probably two branchial ribs with regene- 
rating cilia, were mistaken for tentacula. None of the numerous speci- 
mens occurring to me during a long course of years, exhibited tentacular 
organs in the same position, therefore the real antennular or tentacular 
organs should be substituted in the definition as two bare, triangular, ap- 
proximate spines. In the largest specimens these extend little above 
three lines. Their real use is uncertain. The muddy collections seem 
to be carried up behind, then to fall in front from the extremity ; yet 
no ciliated apparatus has been detected as a conductor on their surface. 
The two exterior or longest branchie of one plume bore some resem- 
blance to antennz, from being of a dark brown colour, while all the rest 
were greenish ; whence transient inspection might have deluded any ob- 
server. Another specimen of larger size, was distinguished by the corre- 
spondence of the dark ruddy brown of the [two] branchiz with the pre- 
ceding, while all the rest were white. But the spinous antennule of 
both were in their proper place. 
On March 28. 1850, I procurred, among others, a full-grown speci- 
men, which quitted its tube. It hada fine plume, rather of light colour. 
But two of the branchiz together, which were quite as large as the largest 
of the rest, were very dark brown. They had much the appearance of 
antennz. But no difference from the structure of the other branchixe 
could be recognised. 
* Miiller, Zoologia Danica, tom. iii. p. 13, Plate LXKX XIX. 
