244 CLAVA SQUAMATA. 



The figures given l)y 0. F. iMiiller, on the fourth plate of his ' Zoologia Danica/ 

 are so characteristic as to leave no doubt regarding the animal to which the celebrated 

 Danish zoologist has assigned the name of Hydra squamata, and must remove all hesitation as 

 to the identity of jMuller's species with that described above, though a nearly allied species 

 described a few years previously by Forskal, under the name of H^dra muUicornis, has been con- 

 founded with the present form, not only by Miiller himself, but by most subsequent writers. 



The first, however, who gave a description of the present species, as has been pointed 

 out by Johnston, was the celebrated Pallas. He discovered it in England, on the shore near 

 Harwich, and under the designation of " zoopliyton minutum corynse simillimum," has recorded 

 it in tiie tenth fasciculus of his ' Spicilegia Zoologica,' published in 1774, accompanying 

 his description with an indifferent figure. 



That the species which Pallas had in view is identical with the Clava squamata of the 

 present Monograph is evident from his description of it : — " Pedunculus hujus zoophyti mollis 

 est intestiniformis, subannulatus eo(\we c/rec/alim dence pluresve simid, passim fucis adherens." 



Pew hydroids equal in beauty and interest this fine species, and most students of the lower 

 forms of marine life will readily accept the estimate of it by the famous author of the ' Zoologia 

 Danica :' — " Aninialium qua3 zoophyta dicuntur, nullum elegantius, observatorique majus gratum 

 esse potuit.'' Attached to the fronds of the olive-coloured seaweeds, it may be seen at half- 

 tides with its clear Venetian-red hydranths, forming soft, flexuous, and pensile clusters, which 

 float passively in the surrounding water as they yield to every motion of the ebbing or flowing 

 current. 



Its proper station being from half-tide to near low-water mark, it may remain for several 

 hours exposed upon the shore to the air and sun along with Coryne pusUla, Laomedeajlexuosa, 

 and Sertularia pumila, which, like it, love the higher regions of the tide range. The hydranths 

 are then much contracted, and lie close to one another, so that the whole cluster, looking like 

 a round, fleshy mass clinging to the seaweed, is enabled to retain sufficient moisture until the 

 returning tide brings the sea again within its reach ; and then the hydranths once more stretch 

 themselves out to their full length, and the entire colony again expands itself in all its beauty 

 beneath the flowing water. 



In every specimen which I have examined in its fully extended state the hydranth, at the 

 l)oint where it springs from the little tubes which form the rudimental hydrocaulus, is much 

 attenuated; soon afterwards it increases in diameter, and then again slightly thins away before 

 it ultimately enlarges into its club-shaped head. Throughout the whole there extends a 

 continuous gastric cavity, whose width varies from distance to distance with the varying diameter 

 of the hydranth, and which, during the contraction of the hydranth, is thrown into close zigzag 

 folds still visible through the surrounding tissues. 



Clava squamata is in perfection dm'ing the whole of the summer months, and then the 

 heavy clusters of gonophores, grouped round the base of the club-shaped head of the hydranth, 

 add greatly to its singularity and beauty. It is strictly moncecious, each tuft-like colony giving 

 rise to gonophores, which are all exclusively male or all exclusively female. 



The adult hydranth in its extended state sometimes shows a slight enlargement of the 

 extreme points of its tentacles, as if these manifested a tendency to terminate in the capitula 

 so characteristic of Coryne and certain other hydroid genera. The terminal enlargement of 

 the tentacles, however, in Clava is entirely transitory and dependent on a particular state of 



