592 A NATURALIST ON THE " CHALLENGER." 



The same purple colouring matter, which is easily distin- 

 guished by means of the spectroscope, occurs in a shallow- 

 water (nine fathoms) Comatula at Cape York, in the tropics, 

 and in a Holothurian, found in 1,955 fathoms, near the Antarctic 

 Sea. Many deep-sea Corals have their soft structures tinged 

 with a madder colouring matter which occurs also in surface 

 swimming Medusae of various kinds.* 



No doubt, in the case of many deep-sea possessors of com- 

 plex colouring matters, these pigments never exercise their" 

 peculiar action on light during the whole life of the animals, 

 but remain in darkness, never showing their colour at all. Just 

 so in the case of many Mammalia, with thick or fur-clad skins, 

 the bright red colouring matter of the blood never sees the light 

 or appears as a red colour. It is only in a few Mammals, that 

 this red colouring matter is turned to account, as, for example, in 

 the white races of man, in which case sexual selection has 

 brought about a tinging of the cheeks by its aid. 



Most deep-sea fish are of a dull black colour, some are white 

 as if bleached. The majority of deep-sea animals are coloured 

 in some way or another, many brightly so. 



zoology and Botany of the ship. — The zoology of "Challenger" 

 itself was rather interesting. At the time that England was left 

 the ship seemed nearly free of animals, other than men, dogs, 

 and live stock required for food. The first Cockroaches ap- 

 parently came on board at St. Vincent, Cape Yerdes, for a large 

 one of these insects was caught by one of the lieutenants on his 

 bed, soon after we left that port. Cockroaches soon became 

 plentiful on board, and showed themselves whenever the ship 

 was in a warm climate. A special haunt of a swarm of them 

 was behind the books in the chemical laboratory, from which 

 Mr. Buchanan in vain attempted to evict them. 



At one period of the voyage, a number of these insects 

 established themselves in my cabin, and devoured parts of my 

 boots, nibbling off all the margins of leather projecting beyond 



* For observations on the Colouring of Deep Sea Animals, see H. N. 

 Moseley, " On the Colouring Matters of various Animals, especially of 

 Deep-Sea Forms dredged by H.M.S. ' Challenger.' " Quart. Journ. Micro. 

 Sci., Vol. XVII, New Ser., p. 1. 



