748 



UErouT — 1884. 



In ronniTtion with llie MilriiLli' invt'sti^rntioiis carrii'd on in tlit> 'Trnvaillcur' 

 nii<l tlitj 'TiiliMUian' liy l*iMl'i',>.s(ir Milno l'!d wards and his iisaociatt'ti, Freneli piivsii). 

 Idf^ists hav»! hiU'lv coninienceil rcscaicia's ou sonio of thi- probleiu.s of deep-stj 

 life. 



Expcrimt'nts Iiavo been rande by M. lu^nianl ' witii a view of dt'torniiniiiR the 

 ellt'cts of iiifj-h iiri'ssuM's, coiTi'Siiuiidin},' with tliosn of the deep wi\, on varium 

 orj.'anisniH. Yeast, after bein^'oxpo^ed to a jinssiire (jf 1,(KK) atmospheres, erjual to a 

 deplli of about 0,r)(K) fiithomsof sea-water, for an lionr, wasmixed with a soluliouoi 

 siipir. An liour elapsed before any signs of fermentation apjteared, an<l a uiixtur- 

 uf \eaat and sn<rar solution did nut ferment at all, wiiilst under a pressure of (JOo 

 atmospheres, eijual to a (h^ptli of about .'{/.MR) fatlioins. Algte, seeds of a pliar.cri). 

 pimic plant, infusoria, and even uiollusca and leeches, were found to lie thrown 

 into a sort of state of sleep or latency by exposun^ to similar pressures, recovering 

 from this condition after a sh<n'ter or longer }ierio(l of return to normal coiKhtions. 

 A iish without a swimming lihulder, or one witii tiie bladder em]itied of air, inav 

 be submitted to a pressure of KM) atmospheres, equivalent to a (le}>tii of (iot^) fiitliomj, 

 without injurious elfect. At L'OO atm()s])]iere8, equivalent to a dei)tli of l,.'!((l 

 fathoms, it becomes torpid, but soon revives when the ])ressure is removed. At 'M 

 atmospheres, equivalent to n depth of about 2,0(X) fatluMus, the fish dies. 



These experiments are of the highest interest. Tiie pressure nuide use of was. 

 obtained by means of water in the absence of air otlier than that aljsorbeJ at the 

 normal atmospliere jiressure, and thus the physical conditions produced AVtire cluselj 

 similar to those actually existent in the deep sea. They are the lirst of their kind. 



Professor r;iul Bert's- somewhat similar experiments related to a ditrerem 

 question altogether — namely, the eil'ect on aquatic organisms of water subjected tn 

 tlie pressure of compressed air. Ho found that young eels were rapidly killed wlieu 

 subjected to a pressure of only 16 atmospheres, and could not survive one of even 

 7 atmospheres for any considerable time.^ lie pointed out the essential diifereiici 

 between the conditions produced in such experiments and those existing in the 

 deep sea, where the charge of oxygen contained by the water has been takeu up at 

 the surface under a i)ressure of one atmosphere ojdy. 



In tlie experiments on animals made by M. Ilegnard's method there is tlie 

 obvious difliculty that the supply of oxygen in the water compressed cannot be re- 

 newed during the experiment, but must be gradually reduced by respiration, and 

 for this reason it would probably be useless, unless a large quantity of water would 

 be employed, to try the eti'ect on a tish of a very gradual application of pressure, 

 extending over many hours. It is probable that the results would be greatly 

 modified if plenty of time could be given for the tish to accommodate itself to the 

 change of pressure, and the conditions in wliich it moves in nature slowly from one 

 de])th to another be imitated. The results of M. Eegnard's further experiments 

 will be looked forward to with great interest. 



A question of the utmost moment, and one that has received a good deal ol 

 attention, is that as to the source of food of the deep-sea animals. (Jertainlya 

 large proportion of this food is derived from the life on the ocean-surface. The 

 debris of pelagic animals sinks slowly downwards, forming on its passage a sparsely 

 scattered supply of food for any animals possibly living at intermediate depths, 

 but becoming concentrated as it were on the bottom. The pelagic animals depend 

 for their idtimate source of food, no doubt, largely on the various pelagic plant.', 

 the range of which in depth is limited by the penetration of sea-water by the sun- 

 light, and probably to an important extent is dependent on tlie symbiotic com- 

 binations of radiolarians witli zooxanthella. 15ut a large part of their food-sup- 

 ply is also constituted by animal and vegetable debris derived from the coasts, 

 either directly from the littoral zone or by rivers and the action of the tides from 

 terrestrial life. Immense quantities of shore-d(5bris have been dredged from deep 

 water near coast*, and deep-sea life appears to diminish in abundance as coasts are 



' P. Regnaid, ' Rcchcrches Experimentales sur I'lnfluence des tr&s-hautes Prcssiccs 

 sur les Organismcs Vivants,' Coviptes-Iiciidiis, No. 12, 24 mars 1884, p. 745. 

 "^ La. Prcssion liarGr.ietriqye, Paris, 1878, p. 814. 

 » Ibid. p. 1151. 



