210 



SCIENCE. 



[Vol. IV., No. 83. 



is of primary importance to the physiologist. It 

 appears from the results of Professor Dittmar's 

 researches into the composition of the ocean-water 

 collected hy the Challenger, that, contrary to what 

 was before suspected, the presence of free carbonic 

 acid in sea-water is an exception. Hence, with re- 

 gard to Mr. Murray's interesting discovery, that, after 

 certain depths are reached, pteropod shells are dis- 

 solved, and disappear from the sea-bottom, and at 

 certain farther depths Grlobigerina shells suffer the 

 same fate, Professor Dittmar holds that the solution 

 is not due to the presence of free acid, but to the sol- 

 vent action of the sea-water itself. Thus the amount 

 of carbonic acid normally present throughout the 

 ocean cannot be inimical to life; but there must be 

 in the depths of the ocean numerous bodies of 

 richly carbonated water. 



French physiologists have lately commenced re- 

 searches on some of the problems of deep-sea life. 

 Experiments have been made by Mr. Regnard with a 

 view of determining the effects of high pressures, 

 corresponding with those of the deep sea, on various 

 organisms. Yeast, after being exposed to a pressure 

 of a thousand atmospheres, equal to a depth of about 

 sixty-five hundred fathoms of sea-water, for an hour, 

 was mixed with a solution of sugar. An hour elapsed 

 before any signs of fermentation appeared ; and a mix- 

 ture of yeast and sugar solution did not ferment at 

 all whilst under a pressure of six hundred atmos- 

 pheres, equal to a depth of about thirty-nine hun- 

 dred fathoms. Algae, seeds of phanerogamic plants, 

 infusoria, and even Mollusca and leeches, were found 

 to be thrown into a condition of sleep, or latency, by 

 exposure to similar pressures, recovering from this 

 condition after a shorter or longer period of return 

 to normal conditions. A fish without a swimming- 

 bladder, or one with the bladder emptied of air, may 

 be submitted to a pressure of a hundred atmospheres, 

 equivalent to a depth of six hundred and fifty 

 fathoms, witbout injurious effect. At two hundred 

 atmospheres, equivalent to a depth of thirteen hun- 

 dred fathoms, it becomes torpid, but soon revives 

 when the pressure is removed. At three hundred 

 atmospheres, equivalent to a depth of about two 

 thousand fathoms, the fish dies. These experiments 

 are of the highest interest. The pressure made use 

 of was obtained by means of water, in the absence of 

 air other than that absorbed at the normal atmos- 

 phere pressure; and thus the physical conditions 

 produced were closely similar to those actually ex- 

 istent in the deep sea. They are the first of their 

 kind. 



Professor Paul Bert's somewhat similar experi- 

 ments related to a different question altogether ; 

 namely, the effect, on aquatic organisms, of water 

 subjected to the pressure of compressed air. He 

 found that young eels were rapidly killed when sub- 

 jected to a pressure of only fifteen atmospheres, and 

 could not survive one of even seven atmospheres for 

 any considerable time. He pointed out the essential 

 difference 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 



taken up at the surface under a pressure of one at- 

 mosphere only. 



A question of the utmost moment, and one that 

 has received a good deal of attention, is that as to 

 the source of food of the deep-sea animals. Certainly 

 a large proportion of this food is derived from the 

 life on the ocean-surface. The debris of pelagic ani- 

 mals 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. A large part 

 of the food-supply is also derived from the debris of 

 the coasts, either directly from the littoral zone, or by 

 rivers and the action of the tides from terrestrial life. 

 Deep-sea life appears to diminish in abundance as 

 coasts are receded from. Unfortunately, our knowl- 

 edge of pelagic vegetable life is very imperfect, and it 

 is to be hoped that botanists may be led to take up the 

 subject. It will then be possible to form a nearer 

 estimate of the extent to which plants are capable of 

 forming a sufficient ultimate food-source for the 

 greater part of tbe pelagic fauna, and, through it, of 

 deep-sea life. The question is of importance; be- 

 cause, if the deep sea derived its main supply from 

 the coasts and land-surfaces in the early history of 

 the habitation of the globe by animals, there can 

 have existed scarcely any deep-sea fauna until the 

 littoral and terrestrial faunas and floras had become 

 well established. It seems certain that the food, as it 

 reaches the deep sea, is mostly in the form of dead 

 matter; and it may be that the long but slender 

 backward-directed teeth of many deep sea fish, re- 

 sembling those of snakes, are used rather as aids 

 for swallowing whole other fishes which have fallen 

 from above, dead, and thus making the best of an 

 occasional opportunity of a meal, than for catching 

 and killing living prey. 



Many interesting results may be expected when the 

 histology of animals from great depths comes to be 

 worked out, and especially that of the special sense- 

 organs. At present very little has been attempted in 

 this direction; principally, no doubt, because deep-sea 

 specimens are too precious to be used for the pur- 

 pose. With regard to the all-important question of 

 the nature of the light undoubtedly present in the deep 

 sea, it is hardly possible to accept Professor Verrill's 

 recent startling suggestion (Science, iv. 8), that sun- 

 light penetrates to the greatest depths with perhaps 

 an intensity at from two thousand to three thou- 

 sand fathoms, equal to that of some of our partially 

 moonlight nights. Such a conjecture is entirely at 

 variance with the results of all experiments on the 

 penetration of sea-water by sunlight, as yet made by 

 physicists, — results which have prevented other natu- 

 ralists from adopting this solution of the problem. 



The progress of research confirms the conclusions, 

 early formed, that it is impossible to determine any 

 successive zones of depth in the deep-sea regions, 

 characterized by the presence of special groups of 

 animals. Some groups of animals appear to be char- 

 acteristic of water of considerable depth; but rep- 

 resentatives of them struggle up into much shallower 

 regions. There are numerous genera, and even spe- 



