94 DEPTHS OF THE OCEAN 



light, but also the proportion of the different prismatic colours 

 at different depths. At the very first attempts the apparatus 

 acted perfectly, and as far down as looo metres at any rate 

 showed light in considerable quantities, whereas at a depth of 

 1700 metres the plates were unaffected even after an exposure 

 of two hours. We may assume accordingly that the amount of 

 light at the latter depth is infinitesimal. The ultra-violet and 

 blue rays are the ones that penetrate deepest. There were 

 plenty of these rays at 500 metres, whereas the effect of the red 

 and green rays there was imperceptible even after an exposure 

 of forty minutes. At 100 metres the rays were of every colour, 

 though red rays were least numerous, while there were rather 

 more green rays, but even at this depth blue and ultra-violet 

 rays predominated. These experiments are of great assistance 

 in dealing with such problems as the growth of plants, for 

 which light is essential, the colours of animals at different 

 depths, and the remarkable modifications in the organs of sight 

 and phosphorescent light-organs that are so characteristic of the 

 higher animal groups in the ocean depths. 



Another haul by night was made at Station 52, though only 

 with four appliances, the deepest of which was at about 600 

 metres. The catches in the tow-nets at the surface and at 30 

 metres were particularly interesting, including a quantity of 

 young fish, amongst which were young fiying-fish and a number 

 of young Scojubresox, many leptocephali, one of which was 

 afterwards found to be a small undeveloped larva of the common 

 eel ; that is to say, a transition stage from the ^gg to the fully 

 developed leptocephalic larva. It was extremely interesting, 

 too, to find eggs of the deep-sea fish Trachypterus at the 

 surface of this deep basin. 



In our deepest appliance we found the beautiful Macrostomias 

 longibarbatus, captured by us at Station 28 in the Spanish Bay, 

 and previously recorded by the " Valdivia " Expedition from 

 the Gulf of Guinea and the Indian Oceart. We also captured 

 a specimen of Opisthoproctns soleatus, as well as a species of 

 Oiieirodes resembling niegaceros (Fig. 81). The haul with the 

 trawl resulted in a take of at least two litres of large red prawns. 



As we had now reached the Sargasso Sea, at Stations 5 1 

 and 52, we set our course northwards towards the island of 

 Fayal, where we intended to coal before crossing over to 

 Newfoundland. While steaming towards the bank which 

 surrounds the Azores, we frequently saw sperm whales, some- 

 times swimming on the surface and easily recognisable by 



