17 



The partitions of the canals arc densely spjeiilose, in addition to the outer 

 felt-work, and a cross section shows that t lie spicules are arranged lor tlie mo,-t 

 part vertically, the cavities conforming to the tubercles on the spi< ule~. 



Structure of the Zooi<l.<. 



The zooids are about 5 mm. in height, and consist of a somewhat slender stalk 

 bearing a cup-like anthocodia, the whole being densely covered with a felt-work of 

 minute warty spindles. The tentacles are short and broad, with a single row of 

 pinnules on each side ; their bases are confluent, so as to enclose a capacious hollow 

 the oral disc, over which they can be infolded. They are not retractile, but 

 when at rest, being infolded, the biserial arrangement of the spicules forms a very 

 primitive operculum. 



The wall of the anthocodia is prolonged into eight triangular lobes, on which 

 the spicules are also arranged biserially, so that each pair forms two sides of a 

 triangle, the enclosed angle becoming more and more obtuse towards the base. 

 This arrangement is continued down to the origin of the stalk, forming a series of 

 ridges on the anthocodia. The triangular projections thus function as a protection 

 to the infolded tentacles. The stalk, though narrow, is very elastic, because the 

 zooid when at rest forms an introvert within it, which in turn sinks within the 

 verruca. The zooid is withdrawn by eight strong bands of retractor muscles, 

 which thus form eight cavities running upwards, and corresponding to the canals 

 in the octagonal disc. These retractor muscles pass downwards and are continuous 

 with the eight mesenteries of the zooid. 



The oral disc is spacious and circular, containing a rather large elliptical 

 mouth- opening, which leads into a keyhole-shaped, richly-ciliated stomod&eum, in 

 which a very distinct sulcus can be distinguished. The ectodermic cells in this 

 region are more numerous and the cilia are longer. 



The mesenteries are all complete, and the muscle banners on the sulcar aspect 

 are easily discernible. The filaments are continued down the stem canals almost 

 to the very base of the colony, while the asulcar filaments show very markedly the 

 ciliated groove so characteristic of the group. 



Ova of enormous size are present in great abundance attached to the mesen- 

 terial filaments. They vary from O'l mm.-0'6 mm. in diameter, but although a 

 considerable number of the larger and more mature ova were stained with borax- 

 carmine, no sign of segmentation could be found, so that the question of viviparity 

 for this genus must remain undecided. 



A fact which may prove to be of great interest is that in every zooid examined 

 there was a large number of Foraminifera of various kinds, and in the decalcified sec- 

 tions examined the protoplasmic contents could be seen surrounded by the ectodermio 

 cells of the stomodseum, while many were also enclosed within the pinnules of the 

 tentacles. When the zooids are at rest, the tentacles are infolded ; and as many 

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