OCR Text |
Show 1906.] ALCYONARIANS FROM ZANZIBAR. 407 by narrow stolons but mainly by a coherent membrane. The polyps may attain a length of 5 mm., not including the tentacles, which are usually about 3 m m . long. The breadth of a fully-extended polyp is slightly under a millimetre. Some of the polyps have their tentacles wholly retracted, ami are themselves contracted into sugar-loaf-like prominences about 3 m m . in height. There is no evidence of calcareous bodies either in tentacles or polyps, and the colour of the preserved specimen is translucent white. The most characteristic features are presented by the tentacles. They measure almost half a millimetre at the base, but narrow somewhat quickly and end in a fine point. They appear to be slightly convex aborally and slightly concave orally. When fully expanded they form a circle about 3*25 m m . in diameter. The pinnules are about nine in number on each side, but the four nearest the base of the tentacle are very short, the longest pinnules being usually numbers 4 and 5 from the distal end ; they are separated from one another by short intervals; and towards the base, beginning at the sixth, there is a gradual shunting from a lateral position on to the oral surface of the tentacle. In shape the pinnules are cylindrical, and have a somewhat rugose appearance due to contraction. In another specimen, which had a red colour when living, some of the polyps attain a length of 10 mm., not including the tentacles, and are densely packed with eggs and embryos. In the majority the tentacles and the oesophageal region are completely retracted within the smooth-walled calyx. In some parts of the colony the polyps are connected by narrow stolons about 1 m m . in diameter ; in others there is a continuous membrane. Locality. Cape Verde Islands. CLAVULARIA PREGNANS, sp. n. (Plate XXX. fig. 3.) This interesting form is well marked by two peculiarities. In the first place, the pinnules occur all round the tentacles. This unusual arrangement is also seen in C. inflata Schenk, but, apart from the generic characters, there is little else in common between the two species. The second peculiarity is that many of the polyps show a large expansion of the body, containing a large embryo or as many as three. There is a thin basal membrane growing over a polyzoon. The polyps, sometimes marked by contraction-rings, are about 5 m m. in length and 1 m m . in breadth, with slender tentacles of 2*5- 3 m m . in length by 0*35-0*4 in breadth. No bare streak is to be seen on the tentacles, which are surrounded by short conical pinnules with a kind of spiral arrangement. Crowded zoo-chlorellse produce here and there a glistening appearance, but no trace of spicules could be seen. Many of the polyps show at a short distance below the tentacles a prominent expansion (2*5 m m . in diameter) of the tube containing up to three embryos. As these grow one side of the |