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 approxi- 

 mate feelers to the genus. As entering its definition in the Sy sterna Na- 

 turce, I am 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 branchiae of one plume bore some resem- 

 blance to antennae, 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] branchiae with the pre- 

 ceding, while all the rest were white. But the spinous antennulae 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 had a fine plume, rather of light colour. 

 But two of the branchiae together, which were quite as large as the largest 

 of the rest, were very dark brown. They had much the appearance of 

 antennae. But no diiference from the structure of the other branchiae 

 could be recognised. 



* Miiller, Zoologia Danica, torn. iii. p. 13, Plate LXXXIX. 



