24 INTRODUCTION TO ZOOLOGY. 



is more remarkable than their power of bearing mutilation, 

 If the tentacula be destroyed, others are soon after formed. 

 If the animal be cut across into two distinct portions, the upper 

 part continues to take food as usual, though for a time unable 

 to retain it. If severed longitudinally, each half becomes per- 

 fect, so that two Actinias are produced; nay, if it be so destroyed 

 that not a fragment is left except a portion of the base, a fresh 

 offspring is soon raised up to fill the place of the parent. 



The following characteristic occurrence is related by Dr. 

 Johnston: " I had once brought to me a specimen of 

 Actinia gemmacea, that might have been originally two inches 

 in diameter, and that had somehow contrived to swallow a 

 valve of 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 the inferior portion of the stomach 

 and the mouth was of course prevented: yet, instead of 

 emaciating and dying of atrophy, the animal had availed 

 itself of what had undoubtedly been a very untoward accident 

 to increase its enjoyments and its chances of double fare. A 

 new mouth, furnished with two rows 

 of numerous tentacula, was opened 

 up on what had been the base, and 

 led to the under-stomach. The in- 

 dividual had, indeed, become a sort 

 of Siamese twin, but with greater 

 intimacy and extent in its unions!' 7 

 Belonging to the same order, but 

 to a different family from the Sea- 

 anemones (Actiniidce), are the Coral- 

 building Polypes of tropical seas 

 (Madrephyllicca) , some of which have 

 been taken in deep water off the 



Fig. 13. CARYOPHYLI.IA. -r> , i J./TTT' io\ rrn 



British coast (Fig. 1 3). Their struc- 

 tures have been the wonder of the navigator and the theme of 

 the poet; and while Science endeavours to reveal the process 

 by which they are upreared, she but adduces another example 

 that, under the dispensations of Providence, the mightiest of 

 works can be executed by the weakest of agents. 



The great extent of some of the coral reefs is very remark- 

 * The common Scallop. 



