324 Transactions. — Zoology. 



nucleated test-cells of small size and with many fibrillae. 

 Everywhere the matrix is occupied by large bladder-cells of 

 slightly granular appearance, and very distinctly nucleated 

 (fig. 3, bl.c. and nc). Towards the middle of the test the 

 bladder-cells are not so distinct in specimens stained in their 

 entirety, but others sectioned before staining show no differ- 

 ence throughout the test, except the absence of bladder-cells 

 from the extremely thin surface-layer. In sections mounted 

 in Canada balsam without staining the bladder-cells are 

 scarcely visible. 



The test above is broken by numerous vacuoles of large 

 size (fig. 1, v.). These form vestibular chambers, into which 

 the branchial siphons of the zooids project, the upper por- 

 tions of the test being apparently never occupied by the ai:ii- 

 mals. A second row of cavities occurs in the lower half of 

 the test. These are the proper zooid capsules, the lower part 

 — that, namely, occupied by the abdomen and upper part of 

 the thorax — being strengthened by the large overlapping cal- 

 careous discs so characteristic of the genus (fig. 1). 



Fig. 9 shows a group of these spicules seen under obj. A. 

 They differ greatly from those figured by Herdman f;-om the 

 two " Challenger " species, being irregularly notched at the 

 edges, and showing no radiating bands. On the other hand, 

 these spicules show more afiinity to -those of the Leptoclinids, 

 &c., for, if we imagine such spicules to be enormously enlarged 

 without increasing the size of their rays, and that these small 

 rays at the same time have their numbers multiplied greatly, 

 we shall obtain a spherical body whose round outline will 

 resem jle that shown in the figure. I regard these projecting 

 lobes as the counterpart of the rays in the Leptoclinids. In 

 some cases the discs acquire a different appearance, illustrated 

 in the upper right-hand member of the group in fig. 9, the 

 closely-set rays forming concentric layers. A third spicule is 

 shown from the edge, exhibiting its lens-shaped form. 



But these spicules, remarkable as they are, do not exhaust 

 our materials as far as the test is concerned. On the contrary, 

 calcareous matter is so strongly characteristic of our New Zea- 

 land forms that the complete investigation of the test and 

 its calcareous deposits alone might afford fruitful study for 

 mouths. 



In a few sections strong calcareous fibres (fig. 1, c.f.) are 

 found in the upper layer of the test. These are extremely 

 difficult to examine owing to their wonderful refrangibility. 

 They appear purplish in colour with picro-carmine, but are 

 white in the natural state, and are visible to the unassisted 

 eye as white threads occurring at rare intervals through the 

 colony. To light them satisfactorily in glycerine or Canada 

 balsam is almost impossible, but, as far as I can make out 



