50 ANEMONES AND CORALS 



other Coelenterates in the possession of a gullet or stomodaeum, 

 mesenteries, and mesenteric filaments. They begin life, on their 

 escape from the parent, as ciliated free-swimming larvae, but in the 

 course of a few hours or days, as the case may be, settle upon some 

 object on the floor of the sea, and at once (if of colonial character) 

 commence the process of budding, which gives rise to the colonies 

 of the adult stage. Nearly all are fixed or sedentary in their habits, 

 though many of the Sea Anemones travel considerable distances - 

 by gliding over the rocks or seaweeds upon which they rest. That 

 some of the Sea Anemones are comparatively long-lived creatures 

 appears evident from the record of one which was taken from 

 the Firth of Forth by Sir John Dalzell in 1828, and which 

 flourished in captivity until August 4th, 1887, when it died. 



The majority of the Anthozoa are dwellers in comparatively 

 shallow seas, though a few have been dredged up from great 

 depths, and they extend from the shores of the Arctic and 

 Antarctic to the warm seas of the Equator. 



The Sea Anemones are such familiar objects of the tidal pools 

 on rocky coasts that they need no special mention here. Atten- 

 tion may, however, be drawn, in passing, to one or two points 

 of interest concerning them. Abundant round the coasts of 

 England, they are almost cosmopolitan in their distribution, 

 attaining their greatest size in the warmer tropic and sub-tropic 

 seas. They are most voracious creatures, killing or paralysing 

 their prey by means of their numerous thread-cells (nematocysts), 

 often becoming greatly and, one would imagine, uncomfortably 

 distended, from the size of the object they have swallowed. They 

 have remarkable powers of replacing lost parts, should some of 

 the tentacles or part of the body be injured or altogether removed. 

 Some are of very great interest, as affording striking examples of 

 that mutual association of different organisms which is termed 

 " Commensalism." Thus there are some Anemones which are 

 always to be found living on a whelk-shell that is inhabited 

 by a hermit crab the two totally dissimilar animals associating 

 together in the most friendly manner. The Anemone, by taking 

 up this position, secures the advantage of transportation from 

 place to place during the hermit crab's wanderings in search of 

 food, and also gains a share of the captured booty ; while the crab 

 gains when at rest, in being partly screened from view by the 



