66 



Another mode of progression is by means of their tentacula. 

 This is perhaps the most rapid of all, but I have never seen 

 any of the animals voluntarily make use of it, except the 

 Luccrnariie; I have placed them on the oral disc and they 

 have travelled with ease and comparative rapidity by using 

 the tentacula, especially the Anthea, which is capable of 

 more variety of action than any of the others. They are 

 said also to distend their bodies with water and allow them- 

 selves to be washed about by the random motions of the 

 sea ; this I have never seen. 



This class of animals, so entirely destitute of solid parts 

 whereby they might perform their various muscular actions, 

 forcibly points out the resources of nature in overcoming 

 difficulties apparently insurmountable. Being so universally 

 soft and gelatinous, no point is offered as a fulcrum on which 

 the muscles can act; but yet a great variety of definite actions 

 are performed with readiness, and are entirely under the 

 guidance of the animal. When they are about to exert 

 themselves, they imbibe water and distend themselves to any 

 extent they please. In this distended state the orifices of 

 the tentacula and all other means of exit are closed, and 

 thus, when the muscles act, they exert themselves on the 

 contained water, which, by resisting, becomes converted into 

 a fulcrum as efficaceous as it is simple. This mode of com- 

 pensating for the want of solid points for muscular action 

 is greatly diffused through the animal kingdom ; instances of 

 its exclusive use are to be found in the Physalia, or Portuguese 

 man of war, where however, air is used instead of water; in 

 the feet of the Asteriadce, and in fact in all the Echinodermata, 

 and in a rudimentary state, in an organ of the highest animals 

 and in man. But this which is so rudimentary and nearly 

 disappears in the higher animals, is the sole means of exer- 

 tion in many of the lower, and the mode of change is at once 

 simple, effective and elegant. 



The appetite of these, like most of the rayed animals, is 

 of the most ravenous kind ; though they can, and have been 

 made to fast for twelve months, yet they are ready at all 

 times for such food as chance or design may offer; shells of 

 the largest size, or the smallest insect are equally welcome. 

 The difficulties into which this great appetite frequently 

 throws them are of the most extraordinary kind. Dr. John- 

 ston mentions one of the Actinia Gemmacea ; the animal 

 originally measured about two inches in diameter, but 

 had contrived to swallow a shell ( Pecten maximus) of the 

 size of an ordinary saucer. "The shell fixed within the 

 stomach, was so placed as to divide it completely into two 

 halves, so that the body, stretched tensely over, had become 

 thin and flattened like a pancake. All communication between 



