136 THE OCEAN WORLD. 



play the part of the fisherman who throws his line, furnished with 

 baited hooks, withdrawing it when he feels a nibble, and throwing 

 again when he discovers his disappointment. These efforts con- 

 tinued in full vigour for two or three days, and I have succeeded 

 sometimes in feeding them with the small crustaceans which swarm 

 on our coasts." 



Of the personfiel of these colonies a few words will not be mis- 

 placed. The common axis of the Agalma is a hollow muscular tube, 

 the length of which may be three feet, and its breadth an eighth or 

 tenth of an inch ; it is traversed by a double current of a granular 

 fluid ; at its summit is the aerial vesicle ; beneath are the swimming- 

 bladders. These are disposed along the trunk in a double series, 

 attaining sometimes the number of sixty ; their structure is analogous 

 to the same organs in Physophora. 



In examining the posterior portion of the trunk, traversing polyps 

 are ob3er\'ed at intervals, whose base is surrounded by a cluster of 

 reddish grains, each of which is armed with a li7ie, and, with its 

 surrounding filament, terminating in a tendril of a red vermilion 

 colour, which is a perfect arsenal of offensive and defensive arms. 

 There we find " sah-es " of divers sizes, and poniards of various forms, 

 the whole constituting a truly formidable stinging apparatus. 



Those warlike engines, those arms of attack and defence with 

 which man surrounds himself. Nature has freely bestowed on these 

 little creatures with which the ocean swarms in some places. It 

 might be said that, after having created these graceful creatures to 

 ornament and decorate the depths of the ocean, the Creator was so 

 pleased with his work that he furnished them with arms for their 

 protection and defence against all attacks from without. 



The family PhysophorifKK includes several genera. Fig. 46 is a 

 representation of Physophora hydrostatica, after ]SI. Vogt's Memoir. 

 We see that the animal is composed of a slender vertical axis, 

 terminating in an aerial vesicle or float, carrying laterally certain 

 vesicles, known as swimming-bladders, which terminate in a bundle 

 of whitish slender threads. 



The aerial vesicle is brilliant and silvery, punctured Avith red 

 spots. The swimming-bladders are encased in transparent and 

 somewhat cartilaginous capsules, which are continued into the 

 common median trunk, the latter being rose-coloured, hollow, and 

 very contractile ; in short, it presents very delicate muscular fibres, 

 which expand themselves on the external surface of each capsule, 

 and is closed on all sides. 



The swimming-bladders are of a glass-like transparency, and of a 



