NoTT. — Oil N.Z. Composite Ascldians. 325 



their structure, they seem to be composed of smaller and more 

 irregular spicules than those forming the capsule, fused to- 

 gether to form long and always straight rods, which seldom 

 branch. 



Next in interest come the peculiar deposits which I have 

 figured in fig. 1 as c.h. These, again, are only local, and are 

 best seen in unstained sections soaked for some hours in clove 

 oil and mounted in Canada balsam. Such sections under high 

 magnification exhibit the radiating branched calcareous skele- 

 ton shown in fig. 1, and given in detail in fig. 7. With this 

 treatment they are extremely distinct, and are seen to be com- 

 posed of immense numbers of small calcareous prisms, crystal- 

 line in appearance, and branching irregularly as in the figures. 



Tet a third form must be distinguished, which is shown as 

 c.h. in fig. 1, and again under obj. A in fig. 4. These "cal- 

 careous trees " are quite crystalline, and are found only in the 

 layer of test in which the zooids are situated, being most 

 numerous near and amongst the calcareous discs. In Canada 

 balsam they are almost invisible, and would certainly be passed 

 over did one not expect to find them. But glycerine j)repara- 

 tions show them with remarkable clearness. Fig. 6 gives a 

 detail view of one of these " trees" as seen in Canada balsam 

 sections with obj. E. 



Closely allied to these latter forms, but quite invisible in 

 balsam, are the crystalline deposits seen in fig. 8, and found 

 only around the zooids. Only one form was seen resembling 

 the figure, but other crystals, reproducing exactly the small 

 branches, are so common that the layer of test just outside the 

 capsule seems to be composed of nothing else. They seldom 

 exhibit more than two or three rays, and recall the form shown 

 in fig. 4 but for their extremely small size. 



Another curious detail in the account of the test is illus- 

 trated in fig. 10. This shows part of a surface view, and 

 throws light upon the network of lighter lines mentioned above. 

 With a high power these lines are seen to be surface vessels, 

 distinct in outline and richly granular, being surrounded by a 

 test - matrix in which are extremely abundant test - cells. 

 Through the upper clear layer a few bladder-cells are visible. 

 Here and there these vessels dilate, enclosing a dark granular 

 body with a central darker portion, also granular. It thus re- 

 sembles a nucleated cell of large size ; but what is its function? 

 This question, as well as the exact relation of the calcareous 

 bodies above to one another and to the test, I must leave 

 undecided, and deal briefly with the zooids. 



These are of large size, and loosely attached in their cap- 

 sules. The mantle is richly muscular, having distinct trans- 

 verse and longitudinal muscle-bands. There is a very distinct 

 thorax and abdomen (fig. 2). 



