104 



THE AUSTRALIAN MUSEUM MAGAZINE. 



swims in a vertical position, u^^ing its 

 back fin as a propeller, but its tail is 

 always on the alert to seize the stem of 

 any plant which it may meet in the 

 water. Using the weed as an anchor to 

 prevent itself from being carried along 

 by moving water, the fish awaits any 

 food which may happen to come along. 

 A curious thing happens when two sea- 

 horses swim against each other; their 

 prehensile tails involuntarily interlace, 

 each gi'ips the other, and it is only with 

 the greatest difficulty that they are able 

 to free themselves again. They have to 

 catch hold of some weed with the under 

 part of the chin and then struggle and 

 pull until the two tails part. 



The sea-liorse shares with the kanga- 

 roo the honour of having an abdominal 

 pouch, and uses it for the same pur- 

 pose. But whereas the young of the 

 kangaroo are not born in the pouch but 

 are placed there afterwards, the sea- 

 horse places the eggs in the pouch and 

 leaves them there to be hatched. The 

 pouch then serves as a shelter for the 

 young. Strange to say, it is only the 

 male fish which possesses a pouch, and 

 he relieves the mother of all i-e- 

 sponsibility concex-ning the upbringing of 

 her offspring. 



Another curious thing about this fish 

 is that it has the power of moving its 

 two eyes quite independently of each 

 other. 



PHOSPHORESCENT AXIMALS. 



If you happen to be at the beach in 

 the darkness of the evening, particularly 

 where the waves break over rocks, you 

 will often see the water lit up by lines 

 and flashes of greenish-white light of in- 

 tense brilliancy. Tlie phenomenon is 

 known of course as phosphorescence. Now 

 on account of this name quite a large 

 number of peoj^le believe that this light 

 is caused by the preseiTce of phosphorus 

 in the watei-. Actually there is no 

 phosphorus in tlie sea at all. The il- 

 lumination is caused by myriads of liv- 

 ing animals called Noctilucae. They are 

 very tiny creatures, almost circular in 

 section, and have a diameter of from 1- 

 20th to 1-lOOth of an inch. Their ap- 



pearance may be compared to that of a 

 microscopic peach made of jelly. On 

 one part of the ))ody, like a projecting 

 stalk, is a kind of tail, with which the 

 little Nocliluca Avhips the w-ater and 

 drives itseK; along. If one of the living 

 animals is touched with a needle point 

 a flash of light is immediately visible, 

 and any irritation makes it reappear. 

 This accounts for the lighting up of the 

 sea near the rocks or as the waves hit 

 the sand; the Ijreaking wave dashes the 

 little creatures against the rough barrier 

 and they flash out their indignation and 

 •give us the phosphorescence. This 

 lighting up may be a kind of self de- 



Sea urchin (Toxocidaris erythrogrammus). 

 The commonest species in and around Port 

 Jackson, sheltering in the crevices of rock-pools 

 in the mid.tidal zone. In the foreground may 

 be seen a few striped periwinkles (Monodonta 

 obtusa) . 



Photo. — A. Musgrave. 



fence with the idea that the bigger crea- 

 tures would hesitate to swallow fire. The 

 light becomes particularly brilliant in the 

 little animal just before it dies, but with 

 death it ceases altogether. 



There is something very queer about 

 this phosphorescence of the Noctilucae. 

 The light is so strong that the illumina- 

 tion from an ordinary tumbler filled with 

 sea water containing the animals is suf- 

 ficiently powerful to enable a person to 



