258 
THE VOYAGE OF H.M.S. CHALLENGER. 
by a distinct enlargement posteriorly, the tip then diminishing to a very dehcate 
point. The edge of the extremity on the ventral aspect (that is, on the side opposite 
the enlargement) is roughened by fine serrations. The twist described by Dr. Macdonald 
is 2 ^robably due to position, and the more slender ones certainly simulate this 
condition. 
The hooks again (PI. XVIIIa. fig. 21) diverge from Dr. Macdonald’s in regard to the 
comparative length of the terminal region, so that in all probability his bristle was from 
the anterior region of the body, where the terminal region is longer. 
In transverse sections of specimens from Samoa, kindly procured for me some years 
ago by Prof. Busk, the body-waU in both males and females is largely distended with 
the reproductive elements. In the males a line of dark brownish pigment runs inside the 
muscular layers, thus surrounding the mass of sperm-cells or spermatozoa which fills up 
the entire cavity. The alimentary canal is atrophied, and forms a median vertical streak. 
The nerve-area is ovoid and comparatively large, no neural canal being evident, though 
it must be remembered that the preservation of the preparations is indifferent. The 
oblicjue fibres pass down by the sides of the cords, and a band on each side goes upward 
to the alimentary canal, apparently enclosing the vessel. 
In the female the stretching of the layers of the body-wall is equally conspicuous, but 
no layer of pigment occurs internally. The nerve-cords, however, have externally a 
deep blackish-brown band. The ova are large and greenish. 
The first scientific account of the Palolo is that of Dr. Gray, who communicated his 
remarks to the Zoological Society of London in February 1847. His description was 
drawn up from numerous specimens (all headless and incomplete) presented to the 
British Museum by the Rev. J. B. Stair. Dr. Gray considered it allied to Arenicola 
(which it really diverges from). He described it as P aloha ^ “ Body cylindrical, 
separated into equal joints, each joint with a small tuft of three or four spicula on the 
middle of each side. Head ? Last joint ending in a couple of tentacles. Eyes globular. 
“ P aloha viridis, n. sp. 
“ Green with a row of round black spots down the middle of the dorsal (?) surface ; 
one spot on the middle of each joint. 
“ Habitat .- — Navigator Islands.” 
In forwarding the specimens from Samoa, Mr. Stair stated that the Annelids appear 
regularly in the months of October and November, during portions of two days in each 
month, viz., the day before and the day on which the moon is in her last quarter. 
They occur in much greater numbers on the second than on the first day of their rising, 
and are only observed for two or three hours in the early morning. At the dawn of day 
they may be felt by the hand swimming on the surface of the water ; and as the day 
nrivances their numbers increase, so that by the time the sun has risen thousands may be 
1 Anri, and Mag. Nat. Hist, vol. xix. p. 409, 1847. 
