SURFACE-SWIMMING FAUNA (INVERTEBRATES). 97 



lines of Velellas that have been stranded in this 

 mariner, and I have seen in Celebes four or five 

 rows of bright blue Physalias stretching for miles 

 along the shore. 



In the Mediterranean and Eastern Atlantic 

 Ocean a very large Physalia occurs which has 

 received the popular name of the "Portuguese 

 man-of-war," and is famous for its stinging 

 powers. The stinging is produced by a number 

 of very minute sacs, which shoot out, when they 

 are touched, a long pointed thread that penetrates 

 the skin and conveys an irritant poison. These 

 are called the thread-cells, and the " Portuguese 

 man-of-war " is not by any means peculiar in pos- 

 sessing them. All the Medusae and Siphono- 

 phores, all the true Corals and Sea-anemones have 

 them in fact, all those creatures which are classi- 

 fied together by the zoologist as Ccelenterata may 

 be said to be stinging animals. The thread-cells, 

 however, vary very much in size in this group, 

 and in the great majority of cases the thread is 

 too feeble to perforate the skin of the human 

 hand, and consequently their owners have not 

 acquired a bad reputation. 



People do not warn their children not to touch 

 the Sea-anemones on the rocks or the Jelly-fish 

 stranded on the beach, and yet they are both 

 dependent for their food upon their stinging 

 powers ; and indeed many of the British Medusae 

 which may be handled with impunity, are capable 

 of stinging quite severely the more delicate skin of 

 the back and arms of unwary bathers. 



Besides the two forms of Siphonophores which 

 [have been described, there are many others to be 

 G 



