16 A NATURALIST ON THE "CHALLENGER." 



was boiled in oil when gathered and this prevented its flying 

 asunder. The fruit I gathered went off with considerable 

 violence when I touched it one day on board ship after it was 

 dry, but it did not make much noise. 



Another Euphorbiaceous tree, the Manchineel, grows in St. 

 Thomas, and its juice is almost as poisonous as that of the 

 " Sand-box " tree. The fable ran that if a man allowed rain to 

 drop off its leaves on to his skin, his skin would be burned and 

 inflamed by it. 



I landed one day on one of the small outliers of St. Thomas, 

 Little Saba Island, about a mile and a half distant from the 

 main island. A puffin (Puffinus sp.) was nesting in holes amongst 

 the grass, laying a single large white egg. The birds allowed 

 themselves to be caught in the nest with the hand. Our 

 spaniels kept bringing them to us, retrieving them with great 

 delight. The island was covered with thorny cactuses. It was 

 impossible to avoid their prickles, and I got covered with them 

 when in pursuit of wild goats and pigeons. There were four 

 kinds of cactuses, a prickly-pear {Opuntia) with spines three- 

 quarters of an inch long ; a quadrangular stemmed cactus, like 

 the most familiar one in green-houses ; a cactus with rounded 

 ribbed stem, growing in candelabra-like form (Cereus), and a large 

 dome-shaped cactus, a foot and a half high and bearing a crown 

 of small red flowers (Ilelocactus). 



The spines must be a most efficient protection to the cactus 

 from being devoured by large animals. I have often noticed that 

 if one approaches one's hand slowly towards some of the forms 

 with closely set long spines, doing it with especial care to try and 

 touch the end of one of the spines lightly without getting pricked, 

 one's hand always does receive a sharp prick before such is 

 expected, the distance having been miscalculated. There seems 

 to be a special arrangement in the colour of the spines in some 

 cases, possibly intended directly to bring about an illusion, and 

 cause animals likely to injure the plant to get pricked severely 

 before they expect it, and thus to learn to shun the plant. Whilst 

 the greater length of the spines next the surface of the plant is 

 white, the tips are dark-coloured or black. The black tips are 

 almost invisible as viewed at a good many angles against the 



