CELLTJLARINE AND OTHER POLYZOA, 319 
in their direction as compared with the avicularia not related to an ovicell ; — 
again in accordance with Levinsen's description. 
The internal avicularium is longer than would be inferred from Levinsen's 
account. Its proximal end is in the same position as that of an external 
avicularium. The side view (PI. 18. fig. 29) shows, in each of two zocecia, a 
pair of avicularia lying side by side. While one of them (f.av.) rises 
normally on the frontal side of the zooecium, the other {i.av.') runs distally 
and basally below the cryptocysf, the avicularium being long and sub- 
cylindrical, and terminating in a beaked rostrum, with an opesia subdivided 
by the projection into it of two calcareous teeth (see Levinsen, pi. 2. fig. 7^). 
In a frontal view (PL 18. fig. 30) the distal end of the internal avicularium 
[i.av.) is seen through the opesia, and its proximal end (j).) forms a slightly 
convex calcareous film, which is partly crossed by the triangular proximal 
end of the cryptocyst (cr.). This overgrowth by the cryptocyst does not 
occur in the external avicularia, which grow frontally from their base. 
Levinsen did not discover internal avicularia in M. ligulata and M. sjncata, 
two species which were associated by MacGillivray with M. robnrata in his 
genus Craspedozoicm (see Sect. II.). I have found them in both these species, 
as well as in M. vectifera, n. sp. (see Sect. V.) and in il/. triseriata. Busk. 
Their occurrence in undoubted species of Menipea is of special interest, as 
indicating that Crasi^edozoum should probably be merged in that genus. 
The internal avicularia do not seem to be common in M. ligulata, but I 
have found them, as shown in PI. 18. fig. 33, in one or two zooex;ia. They 
resemble those of M. roborata, but they appear to be less asymmetrical in 
position. 
In M. spicata (figs. 32, 35) the internal avicularia are considerably smaller 
than in the other two species. They lie closely attached to one of the lateral 
walls of the zooecium, and do not reach its opesia (fig. 35). In side view 
(fi.g. 32) they are seen to pass nearly vertically downwards into the body- 
cavity. The internal avicularia of M. vectifera (fig. 36) resemble those of 
M. spicata. 
In M. triseriata (PI. 19. figs. 41, 42) the internal avicularium is broad and 
short, its distal end being just visible, through the opesia, in frontal view 
(fig. 42). It will be seen from these figures, as well as from one or two of 
those illustrating other species, that a considerable proportion of the internal 
avicularia found occur in the more proximal of the two zooecia formed when 
a longitudinal row is doubled. 
The species in which I have found internal avicularia may all be placed in 
Menipea, s. str., as understood in Sect. V. ; and they constitute a definite 
evidence of affinity in a group of species which can be placed together for 
other reasons. It seems probable that these remarkable structures will be 
found in other species of the same genus, though I have failed to find them 
at present in any but the ones which have been mentioned above. 
