1885.] DR. HUBRECHT ON A NEW PENNATULID. 513 



whole colony feel hard and rigid when handled. Whereas in the 

 stem these calcareous needles — for such they proved to be on micro- 

 scojHC examination (see fig. 14) — are in no way raised above the 

 common level (faint transverse wrinkles being, however, observable), 

 their aspect on the rhachis is considerably different. Here they unite 

 to form projecting polyp-cells, which have the aspect of shields or 

 scales (figs. 4 & 5), but which merge into the proper surface of the 

 rhachis. These apparent scales are moreover provided with two pro- 

 jecting points, well marked in the different figures, aud also wholly 

 consisting of the same needle-like spicules ; whereas tiiey are arranged 

 along the rhachis in what appeared to be faint spirals, ascending from 

 the concave (ventral) side towards the convex (dorsal) one, and 

 directed forwards, i. e. towards the extremity of the scaleless stem. 

 Figs. 6 and 7 show that there are no continuous spirals, but that 

 along the median line of the convex surface the rows of large scales 

 are interrupted by a longitudinal band of very minute scales, answering, 

 however, to the same type, but apparently without any projecting 

 polyps, and which, after KoUiker, may well be called zooids 

 (vide infni). At the top of the stem the polyp-cells have not yet 

 acquired the definite and characteristic shape which is indicated in 

 fig. 5. The few which may here be noticed have a more circular, 

 nipple-like aspect; those just below the top are intermediate between 

 the lateral and the top ones. 



The characters above enumerated are sufficient to raise a strong 

 suspicion that the colony in question is a Pennatulid. Longitudinal 

 and transverse sections of stem and rhachis will enable us to test this 

 supposition by means of the internal anatomy. 



The general inifiression from a transverse section through the 

 rhachis is this, that the colony is much less massive and solid than the 

 external apjjearance aud tlie rigidity would lead us to suppose. We 

 notice a spongy arrangement of large-sized spaces, separated by a 

 system of thin septa and trabeculae (figs. 1 3 & 8), the arrangement 

 of which we shall hereafter have occasion to examine in detail. When 

 touched with the forceps the material that builds up this internal 

 framework is found to be stiff and brittle, and microscopic exami- 

 nation shows that this part of the ccenenchyma is also laden with very 

 numerous calcareous spines (fig. 14), similar in shape to those found 

 in the exterior investment. These spines, though of uniform shape, 

 are of different size. The organic ground-substance in which they 

 are imbedded is moreover stiff and horny, and is dissolved in caustic 

 potash. Together with the calcareous spicules, it gives to the 

 internal framework its rigidity. 



In a section through the stem (fig. 12 and woodcut, p. 515, figs. 1 

 & 2) the arrangement of these septa is seen to be more regular, the free 

 spaces are very symmetrically arranged, and the outer wall is in 

 comparison thicker than in the rhachis. 



Towards the inferior extremity of the stem there is only one 

 transverse septum, dividing its inner space into a dorsal and a ventral 

 half. This septum is seen in a longitudinal section (perpendicular 

 to its plane) in fig. 9. It appears gradually to split into two parallel 



