562 



NATURE 



{Oct. 5, 1882 



reason why they bear the peculiar organs they do, but the food 

 must be so infinitely mare scanty over this intermediate zone than 

 in the upper stratum that life cannot be abundant in it anywhere, 

 and no arrangement such as probably exists at the deep sea 

 bottom whereby unphosphorescent animals profit by the phos- 

 phorescence of others can occur. At the ocean bottom the 

 organic debris falling from above becomes again concentrated 

 and compressed into infinitely less space than in the surface 

 zone, and life in abundance hecoines possible again. The exist- 

 ence of a deep sea fauna at any great distance from coasts 

 depends upon that of a Pelagic fauna overhead. 



With a net capable of acting like that of Captain Sigsbee a 

 vast amount of most interesting investigation lies open. We 

 know as yet next to nothing certain as to the curious oscillations 

 in depth and migrations of the Pelagic fauna. The matter 

 would be a very pleasing subject for research for any yachtsman 

 so disposed, who would care to investigate the movements of 

 the surface fauna of our coasts, and I would urge any here pre- 

 sent to take it up. 



With regard to the connection between Pelagic and Deep-Sea 

 Life, a most important question is the still unsettled one as to 

 the true origin of the Globigerina mud by which so vast an area 

 of the ocean bottom is covered. As is well known, Globigerince 

 and other Foraminifera with calcareous shells occur in abundance 

 at the surface of the ocean. They were originally discovered 

 there by Johannes Miiller, who was the first to observe in the 

 Mediterranean off the French coast the Pelagic Globigerina and 

 Orbulina which are provided with long fine calcareous spines all 

 over their shells, on which to extend their gelatinous tissue and 

 thus by increasing their volume enable themselves to float. Other 

 surface forms are devoid of spines. The well known Globigerina 

 mud is made up mainly of such shells, and the question is whether 

 the main part of this important deposit is derived from the 

 surface, or whether on the contrary the shells composing it 

 belong to animals living on the deep-sea bottom. Mr. John 

 Murray who spent the whole of the Challenger voyage and most 

 of the time which has elapsed since in investigating the surface 

 fauna, and comparing with it the deep-sea deposits writes to me, 

 that he is convinced that in a pure Globigerina mud not 3 per 

 cent, of the carbonate of lime it contains is derive! Irom 

 organisms living on the bottom. On the other hand, Mr. H. B. 

 Brady, the great authority on Foraminifera still seems from the 

 tenour of his slnrt report on the Foraminifera of the Knight 

 Errant Expedition, to hold an opposite opinion, 1 although he 

 evidently wavers somewhat.'- The sarc >de contained in the un- 

 doubtedly living surface globigerina; is tough and readily pre- 

 served in alcohol. It remains firm after the shell has been 

 removed by acids, and may be readily stained with carmine. 

 There is no reason why the sarcode of deep-sea specimens should 

 not be demonstrated with equal ease, yet it is only very rarely 

 that any is found in them, and even then it appears not to be 

 definite and fresh like that so readily procured from surface 

 specimens, and constantly to be seen in other Foraminifera which 

 certainly live at the bjttom. I have never discovered any satis- 

 factory trace of it myself, though I have often sought for it in 

 fresh specimens of globigerina mud. The question whether any 

 form of Globigerina does or does not live on the deep sea 

 bottom is one which still urgently requires a definite answer. 

 The subject of the origin of the Globigerina mud is ably dis- 

 cussed by Butschli, 3 in his account of the Protozoa now in course 

 of issue. One of the principal difficulties in the matter is that 

 much thicker Globigerina shells are found on the bottom, than 

 are met with at the surface. He suggests that the additional 

 thickness may be added to the shell as the animal beconing 

 heavy gradually sinks into deep water out of reach. 



An important geologicalquestion is connected with the deposition 

 of the Globigerina mud. Prof. Haughton, Dr.Croll. and more lately 

 Mr. Wallace in his "Island Life," have nude attempts to arrive 

 at the age of the sedimentary rocks by calculating the time during 

 which a deposit of the mean thickness of the stratified rocks of 

 the globe w-ould be formed on the sea bottom at the present average 

 rate of denudation. In working out this problem Prof. Haughton 

 regarded the materials as spread uniformly over the entire sea 

 bed, whereas Dr. Croll and Mr. Wallace maintain that all the 

 deposit worth consideration may be regarded as taking place 



1 Expliration of the Faroe Channel during the summer of 18S0, by Staff 

 Commander 'lizard, R.N., and John Murray. Free. R. S. Edit:., 1881-82, 

 p. 80. 



* Notes on Reticularian Rhizjpoia {Quart. Joum Miens. Set., 1881, 

 p. 67. 



3 Bronn Klassen u. Ordnungen des Thierreichs, Protozoa, 1880, p. 166. 



within a comparatively short distance of the coast, Mr. Croll 

 believing that the deposit taking place beyond a distance of 100 

 miles on an average is not very great, and Mr. Wallace reducing the 

 area of hypothetical deposition to a very much less breadth. 

 Now both of the latter observers seem to have forgotten that 

 the whole of the organic deep-sea deposits, all over the ocean 

 beds must be taken into consideration in any such calculations, 

 quite as much as any deposits of insoluble silts which may be 

 formed near shore. The vast deposits of calcareous globigerina 

 mud, the siliceous Radiolatian and Uiatomace .us deports and 

 the abundant red clays of the still deeper areas are as much the 

 products of the present denudation of the earth's surface, as the 

 banks formed near the river mouths. There is no other source 

 from w hich they can be derived. A considerable amount of the 

 results of denudation is carried by the rivers -into the ocean in 

 solution, and a further quantity doubtless becomes dissolved by 

 the sea water when the river water is mixed with it, and the 

 Pelagic Foraminifera and other animals assimilating it carry it 

 far from the coasts all over the oceans and deposit it in the 

 deep sea, spreading it evenly over the bottom. 



A large quantity of the sedimentary rocks taken into consider- 

 ation in one side of the calculations referred to, resemble the 

 deep-sea deposits in being mainly ultimately or directly deposited 

 through organic agents. 



I cannot but think that some modification of the results attained 

 in the calculations referred to may be required on this considera- 

 tion, and life allowed to add a few more tens of thousands of 

 years to her age. 



The wdiole existence of the Pelagic fauna depends on the 

 denudation of the land, were it not for this the supply of mineral 

 matter in the sea water would have become exhausted long ago. 



The Pelagic animals prey upon one another largely. The 

 voracity of some of the most harmless looking jelly-like forms 

 i, extraordinary, Dr. Chun describes the Ctenophor Beroe as 

 swallowing another Ctenophor much larger than itself with the 

 greatest rapidity distending its body enormously in the act. Many 

 of the larger pelagic animals, like the whalebone-whale, feed on 

 large quantities of mmute animals, Prof. Steenstrupp has found 

 that certain Pelagic Cephalopods feed on minute Crustacea 

 and the use of the wide conical membrane surrounding the arms in 

 the Cirrhoteuthidse is apparently to catch shoals of Entomostraca. 

 Similarly the Penguins of the southern sea seem to feed largely 

 on minute Crustacea. Their stomachs a\*e to be found crammed 

 with them. In catching them they move through the water with 

 immense rapidity, and all such feeders are endowed with immense 

 muscular power. Other pelagic Cephalop, <ds may lie seen at the 

 surface in droves pursuing shoals of fish and squirting the water 

 from their funnels into the air in small jets in all directions. 



A most remarkable fact is that certain larval forms of shore 

 animals undergo extraordinary modifications under the influ- 

 ence of Pelagic existence. The best known instance in point 

 is that of the Leptocephali, which are small ribbon-shaped 

 fishes absolutely transparent, and in many cases devoid of 

 any haemoglobin in their hi >od, whilst the slight skeleton they 

 possess is cartilaginous only, and the whole tissues are soft and 

 pulpy. They are often abundant at the sea surface far from 

 land, but are never found sexually mature. There seems to 

 be no d >ubt that the most abundant of these forms are the young 

 of conger eel-, but off many coasts, as for example, that oi Nor- 

 way, where congers are abundant, n > Leptocephali are ever 

 fo.ind. Dr. Giinther's conclusion is thatvall these curious fish 

 are the results of the abnormal development of the larva of various 

 li-hes (possibly sprung from eggs accidentally shed at the sur- 

 face instead of the bottom), which continue to grow to a certain 

 size without corresponding development of their organs, and 

 perish without ever becoming mature. 



Another instance of similar modification is that of the young 

 flat fish termed l'lates-ae, which are like the Leptocephali per 

 fectly transparent. These are also often taken in the open ocean 

 and it appears probable that when thus placed under unnatural 

 circumstances their development becomes arrested, and many 

 probably perish eventually, like the Leptocephali, without the 

 arrangement of their eyes ever becoming unsymmetrical. The 

 deep sea is devoid of flat fish and it seems impossible that the 

 larva; should ever find their way back to shore. 



In the case of the young of the Flying Gurnet something 

 analogous occurs. In the minute young a reversion to the 

 ancestral condition is exhibited, the pectoral fins are not longer 

 in proportion to the fishes' body than those of other fish, they 

 only begin to develope into wings when growth has proceeded 



