Chap, xxii.] VEGETABLE DEBRIS AT GREAT DEPTHS. 505 



It might be supposed that these shells and other surface 

 animals would consume so long a time in dropping to the 

 bottom in great depths that their soft tissues would be decom- 

 posed, and that they would have ceased to be serviceable as 

 food by the time they reached the ocean bed. Such is, how- 

 ever, not the case, partly because the salt water of the sea 

 exercises a strongly preservative effect on animal tissues, partly 

 l)ecause the time required for sinking is in reality not very 

 great. 



In order to test the matter for myself I made the following 

 experiment. I took a dead Salpa, of about 2 inches in length, 

 and placed it in a glass cylinder full of water, and 3 inches in 

 diameter. I allowed the Salpa to fall from the surface of the 

 water in the cylinder to the bottom a number of times, and 

 noted carefully the time which it took to traverse this distance, 

 which was about 8 inches. I found that on an average it took 

 20 seconds to fall the 8 inches. This gives at the same rate, 

 without allowance for acceleration, a distance of a fathom to 

 be traversed in three minutes, or 2,000 fathoms in four days 

 four hours. ^ c\ta^i*y- 



I allowed the Salpa to remain in tlie sea water in the cylinder t-^^-^t-w^ 



for a long time. It was still not greatly decomposed after 

 having remained in the same water for a month, whilst the ship 

 was in the tropics ; the nucleus was after this interval still 

 undestroyed. The dead animal might have thus sunk to the 

 bottom in the greatest depths almost six times over without 

 having become so much decomposed as to be unserviceable for 

 food to deep-sea animals. 



We obtained by our dredgings several interesting proofs 

 of the feeding of deep-sea animals on didris derived from 

 neighbouring shores. Thus, off the coast of New South AVales 

 we dredged from 400 fathoms a large Sea-Urchin which had 

 its stomach full of pieces of a Sea Grass {Zostera) derived from 

 the coast above. 



Again, we dredged between the New Hebrides and Australia 

 from 7,400 fathoms, a piece of wood and half a dozen 

 examples of a large palm fruit as large as an orange. In one 

 of these fruits w^hich had hard woody external coats, the 

 albumen was still preserved and perfectly fresh in appearance, 

 and white, like that of a ripe cocoanut. The hollows of the 

 fruits were occupied by a small Lamellibranch Mollusc and a 

 Gasteropod, and the husks and albumen were bored by a small 

 Teredo or allied Mollusc. The fibres of the husks of the 

 fruits had amongst them small Nematoid Worms. 



We dredged up similar land vegetable debris on many other 

 occasions, of which I will cite some, because they are interest- 



