A CONTRIBUTION TO THE ANNELIDA. 73 
segments existed they were well developed ; whereas in another 
with forty-five to fifty segments they were not longer than the 
others. 
The geographical distribution of this larva is extensive, and 
Claparéde gives a figure of one from Christiansand which for the 
most part corresponds. He does not know any adult Annelid 
with longer feet from the seventh to the eleventh, nor with the 
peculiar spinose bristles, which are probably provisional organs 
The peculiarity is that they existed so long. 
The most advanced larva procured by Claparéde was thus 
only supplied with short tentacles, that is, little more elongated 
than in Pl. 8, fig. 4, of the present paper; whereas several 
procured at St. Andrews in October had these organs consider- 
ably elongated—stretching backward to the fifth (Pl. 8, fig. 5) 
and even to the eighth bristled segment. They are large and 
comparatively massive organs resembling those of the S pio- 
nid. The unpaired process in front is considerably shorter 
than that figured by Busch,! and Claparéde and Mecznikow,? 
in the larval Nerine cirratulus. Perhaps it only develops 
in the later stages, for in Pl. 7, fig. 7, it is not visible in a 
lateral view. Moreover, several with long tentacles had shorter 
bristles than in the earlier stages. The tail terminates in a 
somewhat ovoid tip with a dimple in the centre and a ring of 
cilia towards the tip (Pi. 7, fig. 8). In lateral view, however 
(ibid., fig. 9), the tip occasionally assumes a conical condition. 
A dorsal and a ventral blood-vessel (Pl. 8, fig. 6) are evident 
in the same view (lateral). The conspicuous pigment-speck 
between the bases of the feet is either opaque white or yellowish 
white, and is often finely ramose. Towards the end of October 
(23rd) an advanced example had peculiar globules which re- 
fracted the light like oil along the lateral region (Pl. 8, fig. 7) 
from the tenth foot backwards. They were absent from both 
dorsal and ventral aspects till near the tip of the tail. Their 
Beobachtungen iib. Anat. u. Entwicklung. &c.,’ p. 65, Taf. viii, 
figs. 1—4. 
2 « Beitrage zur Kenntniss der Entwickelung. der Chetopoden,” ‘ Zeit. 
wiss. Zool.,” Bd. xix, separ. Abdr., p. 11, Taf. xii, fig. 4. 
