THE AUSTRALIAN MUSEUM MAGAZINE. 



21 



enemies or exert a numbing- effect on the 

 animals upon which it preys. The lower 

 branch of the tentacle, which is used for 

 crawling, ends in a sucker-like extremity. 

 By means of these suckers and their 

 secretion the animal is able to adhere so 

 firmly to the smoothest surface that it is 

 very difficult to detach it. 



The most striking feature of the animal 

 is its mode of progression. Ordinarily a 

 jelly-fish floats in the sea with the tentacles 

 hanging downwards, or it swims by con- 

 tractions of the powerful muscles on its 

 under surface, which drive out the water 

 of the umbrella and send the animal for- 

 ward in the opposite direction. In the case 

 of the creeping or crawling jelly-fishes, the 

 tentacles are modified into ambulatory 

 organs, by means of which the animal 

 moves actively over the surface of a sea- 

 weed or other marine growth. When the 

 jelly-fish is lightly touched on one side, 

 the crawling movement can be readily 

 observed ; the tentacles on the side opposite 

 the source of irritation are released and 

 applied at a point further from the body, 

 which is then moved in this direction. Pro- 

 gression is also assisted by a re\erse move- 

 ment of the tentacles on the other side. 



.Another characteristic and almost con- 

 stant movement is exhibited by the ten- 

 tacles. This movement consists of a sud- 

 den jerking upwards, so that the upper 

 branch of the tentacle, with its batteries 

 of stinging-capsules, is thrown over the 

 body, the lower or sucker-bearing branch 



at the same time loosening its hold on the 

 substratum and sharing in the upward 

 movement. It has been suggested that this 

 action may have some protective function, 

 since by it the clusters of stinging-capsules 

 are thrown over the upper surface of the 

 body. This movement is maintained al- 

 most constantly when the animal is 

 stationary, and differs entirely from the 

 slow and deliberate movement of crawling. 



Crawling jelly-fishes are not known to 

 swim, except the Falkland Island species, 

 which is apparently able to do so. The 

 species from Port Jackson was never ob- 

 served to swim ; neither could any swim- 

 ming motion be induced by dropping the 

 specimens into sea-water. They would fall 

 straight to the bottom of the vessel and 

 then move along the surface of the glass 

 liy slow crawling movements. 



The small jelly-fishes or medusa; are 

 really special bodies carrying the generative 

 organs. They originate as members of a 

 fixed, usually branched, plant-like animal 

 or "Zoophyte," from which they are set 

 free l)y breaking away as little umbrella- 

 shaped l)odies. These individuals differ 

 widely from the fixed form, being, indeed, 

 so unlike it that their origin would never 

 have been guessed if the separation had 

 not been seen to take place. 



The discovery of a crawling jelly-fish in 

 Port Jackson is, therefore, extremely in- 

 teresting, but up to the present this one 

 has not lieen traced to its fixed form. 



DYING SLOWLY.— A Sea-egg or Heart 

 L'rchin, Brcynia, which buries itself in the 

 sand of the lagoon at Lord Howe Island, 

 can withstand an amazing amount of injury 

 and still live. If its shell or test be broken 

 open, it is seen to be filled with little more 

 than a membranous gut distended with 

 mud, and a few reproductive organs. The 

 removal of these inner works, however 

 roughly, seems to cause the animal but little 

 pain, since it merely waves its many spines 

 around in feeble protest, and if given the 

 opportunity, will dig itself into the sand 

 again as effectively as though its vital 

 organs were all in their proper places. 



Several specimens which were being pre- 

 pared for museum purposes had all of their 

 soft parti removed except the extremely 

 thin membrane which lines the test, yet 

 they waggled their spines around freely for 



at least half an hour afterwards, the move- 

 ment becoming quite frantic when they were 

 finally immersed in fresh water. One wan- 

 dered around a flat board upon the tips of 

 its spines, apparently searching for its well 

 beloved sand beneath the lagoon waters. 



Heart LVchins, so lowly in organisation, 

 are evidently but little affected by what we 

 more sensitive beings recognise as pain, and 

 consequently die very slowly from injuries 

 which would instantly destroy more highly 

 organised animals simply through the shock 

 to their nervous systems. But though so 

 lowly, they nevertheless construct amazingly 

 intricate shells for the protection of their 

 soft parts, their apparently simple mem- 

 branes secreting wonderfully complex and 

 ornate plates which interlock so accurately 

 that an examination of them leaves us lost 

 in admiration. — .A. R. McCulloch. 



