OF THE PORTUGUESE MAN-OF-WAR. 559 



from which the splendid colours, and the acrid fluid covering 

 the surface, as well as the ordinary supply of nutriment, are 

 derived. 



It has been a general opinion that the air in the cavity of 

 the body is collected at the will of the animal, and that it can 

 be expelled at pleasure, or through fear of danger. Neither 

 of these ideas, however, appears to be accurate ; for in regard 

 to its accumulation, it is clearly not received from without, 

 and as to the power of expulsion in any manner of haste, es- 

 pecially in storms, and to enable it to sink from danger, com- 

 mon observation proves the contrary ; for they are seen float- 

 ing on the most turbulent waves, and are frequently thrown 

 ashore in tempests. Examination, indeed, cannot fail to per- 

 suade any one that a creature with so little of solid substance 

 in its composition, cannot be made to sink without the almost 

 total expulsion of its air, which ordinary mechanical com- 

 pression does but little towards effecting ; and when this ex- 

 pulsion is procured by puncture, which may amount to what 

 the creature can effect by great effort, the animal may be made 

 to shrink into a comparatively small compass, without at all 

 approaching to a condition in which it can sink below the 

 surface. I have discharged nine-tenths of the contained air, 

 thereby causing a shrivelling of the external membrane, with- 

 out bringing it to a state in which it did not swim buoyantly 

 on the water. 



But an examination of the Physalia when in undisturbed 

 liberty will show that the real use of the inflated condition is 

 not buoyancy alone. The accumulation of air will then be 

 seen absolutely necessary as a fulcrum or point of support for 

 the action of the muscular structure ; and accordingly, the 

 creature, by the contractions of portions of its surface and the 

 relaxations of others, projects the oral extremity into the form 

 of a snout, lifts or moves it towards either side, and depresses 

 portions of the centre, lengthening or shortening itself, and 

 especially dilating towards the side from which the tendons 

 are dependant, according to its pleasure. But perhaps none 

 of its actions are so capable of displaying the management of 

 a complicated intention, as those by which the animal con- 

 trives to fall on its side from its more usual position with the 

 crest aloft. The anterior portion is first dilated, by which a 

 basis is formed capable of sustaining the whole bulk : the 

 hinder part, for about a third of the length, is then rendered 

 slender and elevated ; in which condition but little of the sur- 

 face is immersed, and a very small degree of inclination to 

 either side causes it to fall over, with the crest on the surface 



