8 THE VOYAGE OF H.M.S. CHALLENGER. 



right or an acute angle with the next node, a condition which has induced Verrill, in his 

 diagnosis, to make use of the expression " furcately branched." The branch of 

 Dcmjgorgia agassizii figured in Verrill's work cited above (pi. ii. fig. 4), shows the law 

 of branching signified, only the twigs come off from the branches at acute angles. 

 The accompanying woodcut is to illustrate this law of branching. 



Fig. 1. — Mode of branching in Dasyijorgia. 



The polyps are large in relation to the twigs which bear them. Their form is 

 cylindrical, somewhat enlarged towards the base ; their diameter is always greater than 

 that of the supporting twigs. The oral portion, with tentacles, is not retractile ; in repose 

 the tentacles are simply folded together over the oral disc, and protect the oral region 

 by means of the spicules situated in their dorsal portions. 



In some species the polj^s are sparingly scattered on the stem, and on the branches 

 and twigs, so that there are never more than two polyps on a node. The end polyp 

 of the last twig is never apical. The jjoint of the twig always projects beyond the base 

 of the laterally placed polyp. In addition to the tentacle-bearing polyps there are in 

 some species slightly conical zooids without tentacles. Spicules are present in the thin 

 coenenchyma, in the polyps and in the tentacles, completely filling the outer sides of 

 the latter, while they are absent in the surfaces turned towards the mouth, as well as in 

 the pinnules. There are always two layers of difi"erently shaped spicules. Those of the 

 outer layer are in some species {Spiculosie) long and spindle-shaped, somewhat flattened 

 spicules, blunt at the ends and provided with a fine sculpturing, in the form of little wart- 

 like projections. Large in the polyps, on the dorsal part of the tentacles they take the 

 form of smaller spindles, which lie side by side in from two to four rows, and overlap 

 one another on opposite sides. On the calyx they are arranged longitudinally. The 

 spicules of the coenench3'ma are usually somewhat difi"erent from the spicules of the 

 polyps, sometimes larger and sometimes smaller than these. In some other groups, 

 which may be distinguished as Squamosa^, the spicules are flattened, almost scale-like, 

 covering each other. Their edges are often finely toothed, frequently lobate, and from 

 the teeth run fine concentric furrows to a small nucleus. They form, on the tentacles, 

 from one to three rows. On the calyx they are placed either obliquely to its long axis 



