Oct. 5, 1882] 



NA TURE 



559 



Baron von Richthofen (one of a series on Eminent Geographers) 

 besides several other papers, and notes on political geography 

 and statistics. The Rundschau is edi.ed by Prof. Unilauft, and 

 published by Hartleben of Vienna. 



The steamer Louise relumed to Hammerfe-t on October 1 

 from the southern part of the Sea of Kara. The Captain report- 

 that, owing to the prevalence of a hard frost and the consequent 

 accumulation of ice, vessels are unable to pass. The Louise left 

 the Dani-.h exploring vessel-, I'arna an I Djimfha, on Septem- 

 ber 22, ice-bound, at a point eighty miles to the east of the 

 i-land of Waigatz. All was well on board, and hopes were 

 entertained that they would shortly be set free. 



In the October number of the Proceedings of the Royal Geo- 

 graphical Society, the leaiing papers are on the Cameroons 

 District, \Yest Africa, by Mr. George Grenfeld ; and on the 

 Coast Lands and some Rivers and Ports of Mozambique, by Mr. 

 H. E. O'Neill, H.B.M. Consul, Mozambique. From the Notes 

 we learn that Mr. II. 'Whiteley, who has devote \ himself for 

 many years to natural history pursuits in the interior of British 

 Guiana, has just returned to England. He resided for upwards 

 of a year among the Indians in the neighbourhood of the famous 

 Mount Roraima, of which in its many aspects he made a 

 numerous series of drawings. The number, we may say, con- 

 tains a full report of the import tnt paper on the Deserts of 

 Africa and Asia, read by M. Tchihatcheff at the Southampton 

 meeting of the British Association. 



PELAGIC LIFE^ 



A S used technically by naturalists, the term "Pelagic" applied 

 ■"■ to living things denotes those animals and plants which 

 inhabit the sm face water- of the seas and ocean-, fust as the 

 land surfaces, the sea shores, and the deep ocean beds are each 

 tenanted by assemblages of organisms specially adapted to the 

 conditions of existence there occurring, so the surface waters of 

 the oceans are inhabited by a characteristic fauna and flora. 

 The special modifications in structure which the member- com- 

 posing this fauna and flora exhibit as adapting them to their 

 peculiar envir inment are of a most interesting and remarkable 

 character : and it is concerning the nature of the Pelagic fauna 

 and flora, the mutual relations between the two, the strange 

 forms which Pelagic animals assume, their curious habits of life, 

 their zoological ami geological importance, that the present lec- 

 ture on Pelagic Life will consist. I have spoken of pelagic life 

 as belonging to the surface waters of the oc;ans becau-e it is in 

 the superficial strata in which it appears to be most fully deve- 

 loped ; but, as we shall see in the sequel, it is impossible as yet 

 to limit definitely the range of pelagic forms in depth, and we 

 shall even have to refer to some connections of the fauna of the 

 deep ocean bottom with that of the surface. 



Pelagic life then includes the inhabitants of the whole ocean 

 waters, excluding th.se belonging to the bottom and shores; 

 that is to say, the inhabitants of an area equal to nearly three- 

 quarters of the surface of the globe. And it may tend to enhance 

 our appreciation at the outset of the importance of the pelagic 

 fauna if we reflect that in point of numbers pelagic animals 

 probably far exceed all others existing. The extraordinary 

 abundance of life, as seen at the surface of the ocean under certain 

 circumstances, when the water is often discoloured for miles and 

 its surface strata absolutely filled with small animals, has often 

 been described by voyagers, but can never be fully realised till 

 it is actually witnessed. 



The existence of pelagic animals at all is directly dependent on 

 that of pelagic plants. No animal life can exist without vegetable 

 food as a basis, and the first living substance which came into 

 existence must have been cap ible of constructing protein for itself 

 from inorganic sources, and been physiologically a plant. Now, 

 in many regions the sea-surface teems with vegetabl life. In ihe 

 Polar waters diatoms swarm, sometimes occurring so abundantly 

 that they render the water thick like soup, and being washed up 

 on the ice in the Antarctic regions, colour it brown, as Sir 

 Joseph Hooker showed. When a fine net is towed overboard 

 amongst them, they fill it with a jelly-like mass that, when 

 squeezed in the hand, leaves behind their skeletons, a mass of 

 line silica like cotton wool. In the temperate and warmer seas, 

 diatoms, though still present, are scarcer, and their place is taken 



' Address at the Southampton meeting of the British Association, August 

 2 . 8, by H „ N ; Mosele y. f'.K.S., Professjr of Human and Comparative 

 Anatomy, Oxford. 



by other simple minute algae, mainly Oscillatoriae. As we passed 

 through the Arafura Sea between Australia and New Guinea in 

 the Challenger Expedition, the whole sea for several days' voyage 

 was discoloured far and wide by such alga;, and smelt like a reedy 

 pond ; and in the Atlantic we passed for days through water 

 full of minute algae (TrichoJemium) gleaming in the water like 

 particle- of mica. From these fine alga; the simpler animals, on 

 which the higher animal forms subsist, derive their food. No doubt 

 the food-supply is largely supplemented by organic debris of all 

 kinds drifed from shores, and by floating sea-weeds, certain 

 species of which, like the gulf-weed, grow in a pelagic condition. 

 Coccospheres and Rhabdospheres may very possibly be of vege- 

 table nature, an I contribute to the pelagic stock of food, together 

 perhaps with some of the Cilio-flagellata, such as Ceratium, 1 

 which may prove alsi to be physiologically vegetable. How- 

 ever, in many parts of the ocean vegetable organisms are not 

 markedly abundant, and it had always seemed to me that the 

 ultimately pelagic food supply was scarcely as abundant as it 

 should be to account for the vast extent of pelagic fau ta, until 

 the recent establishment by Dr. Karl Brandt, of the existence of 

 the curious condition of mutual relations of certain animals and 

 plants known as symbiosis. 



It is found that amongst the tissues of certain animals 

 there are constantly imbedded quantities of unicellular algae. 

 These alga; are not to be regarded as parasites, but a relation 

 of mutual benefit exists between them and the animal with 

 which they are associated ; they are nouri-hed by the waste 

 products of the animal, whilst the animal thrives on the com- 

 pounds elaborated by the.n and the oxygen they set free. Such 

 an association of mutual benefit is termed symbiosis, and it 

 was in the case of same of the most abundant of pelagic animals, 

 the Radiolarians, that the true nature of the algre in question was 

 first discovered by Cienkowsky. I shall throw on the screen a 

 figure of one of these Radiolarians Coll ozoum inerme. It consists of 

 a rounded mass of jelly traversed by fine radiating pseudopodia 

 with a central spherical sac or capsule, and in the interior of 

 that a large oil globule. One function of the oil globule apparently 

 is to float the animal at the water's surface. The animal has the 

 power by some means of rising or sinking at will, probably by 

 means of a modification in the size of the oil globule. Embedded 

 in the jelly outside the capsule are seen conspicuous bright yellow 

 cells, one of which is shown in the act of dividing. These cells 

 contain starch, and are the unicellular algae, which Brandt has 

 termed Zooxanthellae. It is obvious that a compound organism 

 such as this is self-supporting, requiring no external source of 

 organic food ; and it would be quite possible to conceive the 

 existence of a vast pelagic fauna having Radiolarians combined 

 wdth their Zooxanthellae only as a basis. The single organism here 

 represented on the screen is not larger than a pin's heal. In the 

 living condition thousands of such are united, clustered together to 

 form little bolsters of jelly about half an inch long, and on calm 

 days on the ocean the whole surface water may be seen full of 

 such masses for miles and miles, as far as the eye can reach, 

 forming a vast supply of self-supporting fool for other pelagic 

 organisms. It is probable that the symbiotic condition in Radio- 

 larians is of great importance in the general economy of pelagic 

 life. There are other pelagic animals, for example, Ctenophora, 

 in some of which unicellular algae are similarly present. 

 Symbiosis may possibly have been more common amongst 

 pelagic faunas of earlier geological epochs, when diatoms appa- 

 rently were not abundant or nm-existent. The Radiolarians are 

 characteristic members of the pelagic fauna. Most of them are 

 provided with most beautiful siliceous skeletons, as, for example, 

 Rkizospccra leptomita, now on the screen. It is, as may be seen, 

 provided with a stock of Zooxanthella like Collozoum. 



Animals are pelagic in very various degrees, and may be placed 

 under a series of categories accordingly. There are the pelagic 

 animals far excellence, those that are found at the greatest distances 

 from shores, and which are capable of passing their whole exist- 

 ence there, and are floated only accidentally to land. Such are 

 the Radiolarians, Siphonophora, very numerous Crustacea, Al- 

 ciopa, Tomopteris, Heteropods, lanthina, Pteropods, the Pelagic 

 Cephalopods, Salpae, and Pyrosoma, and numerous pelagic fish. 

 These might conveniently be termed eupelagic. Then there are 

 others, such as many Scyphomedusae and most Ctenophora, which, 

 though thoroughly pelagic in habit, are met with in greatest 



1 Mr. John Murray has observed that species of pelagic ceratium are to be 

 met with, often forming long chains, composed of individuals united in linear 

 series. I observed an instance of the same fact myself. It seems to give 

 some additional indication of the possibly vegetable nature of certain 01 the 

 Cilio-fiagellata. 



