82 MR. A. W. WATERS ON 
gigantically developed, to which d’Orbigny referred when he 
wrote “‘pourvus latéralement de cellules plus grandes formant 
une partie dentée” (PI. 10. fig. 19). These gigantic avicularia 
have not been found in P. saccata, B. A sketch of the colony 
(which I should call a memorandum sketch) to give an idea of the 
growth is reproduced, but this is not an exact drawing (PI. 11. 
fig. 1). D’Orbigny’s species either must stand for the cylindrical 
form, or, not having been recognized, becomes P. perpusilla, B., 
being of course closely allied to P. saccata, B.; but there seems 
sufficient reason for separation. Unfortunately Busk’s figures 
and descriptions of P. saccata are far from satisfactory. 
Another specimen marked in pencil “13622 Terre Neuve, 
Eschara elegantula” is probably a mistake, and was not so 
marked by d’Orbigny. 
Fischer unites 2. pavonina, VOrb., with Porella elegantula, 
d’Orb., but the specimen 13621 from the Ie de Ré is flabelliform 
(fig. 2, Pl. 11), with avicularian chambers smaller than those in 
P. saccata, and also has the ovicells imperforate and not much 
raised, 
The Arctic specimens of P. saccata which I have examined 
start from a broad base, and the colonies grow to 3-4 inches in 
height, with compressed branches about 4 millimetres broad ; the 
branches often gradually curve round, so that they are not all 
in one planeas described by Busk in his ‘Challenger’ specimens. 
On the front of the zocecium, near the proximal end, there are 
two pores which open into the avicularian chamber (fig. 14, 
Pl. 10). These are shown by Smitt in his figure 143, which 
seems to be from a worn specimen. The pores are not always 
seen when the zocecium is covered by the exterior membrane, but 
in specimens boiled in caustic potash and in sections these pores 
can be made out, and they canalso be distinguished in d’Orbigny’s 
specimen of P. elegantula from Newfoundland, and readily in the 
‘ Challenger’ specimens. 
Sections show that there are very large oral glands which are 
placed nearer the basal (neural) wall than are the tentacles, that 
is they are underneath the tentacles, which is not a usual position 
for the glands. The cells forming these glands often have large 
vacuoles, and the contents of the glands are the same homogeneous 
unstainable material which we have seen in other glands. No 
avicularian glands were found. Specimens from near Wilezek 
Land, collected 16th or 17th July, 1897, have well-developed 
ovaria and testes. 
