394 



NATURE 



[August 23, 1883 



RESEARCHES ON THE DEEP-SEA FAUNA 

 FROM A ZOOGEOGRAPHICAL POINT OF 

 VIEW 



TOURING recent years surprising and very remarkable 

 -»-"' discoveries have been the result of expeditions 

 despatched from various countries by official and private 

 bodies, in order to examine the zoological condition of 

 the oceans of the globe. Thus, below the line of three 

 hundred fathoms' depth, where biologists for many years 

 believed with Edward Forbes that all animal life ceased, 

 a fauna rich both in forms and individuals has been 

 brought to light, and the theories once common enough 

 among savants of a total absence of life at a certain 

 depth in the sea have thereby in two decades suffered 

 a complete revolution. Many objects which had pre- 

 viously been looked upon as biological impossibilities 

 have been discovered, and the systematic science of zoo- 

 logy has been enriched with copious materials, from 

 which hitherto unknown animal varieties have been de- 

 scribed, recorded, and placed in their true position in the 

 system, whereby many a gap in the zoological scale has 

 been filled up, and' science in a remarkable space of 

 time made rapid progress. Besides this merely scientific 

 gain, which can only be fully realised by men of science, 

 the zoological museums have obtained valuable and fruit- 

 ful treasures. The researches of the fauna of the oceans 

 have been of double advantage, viz. as both enriching 

 science and museums, and zoologists are delighted at 

 both. The interest which various countries have taken in 

 the study of the fauna of the sea has been share! between 

 England, the United States, Sweden, Norway, and Hol- 

 land, while lately even France and Italy have taken steps 

 to assist in promoting this branch of biology, and there 

 can be no doubt that similar researches will in the imme- 

 diate future be carried on as indefatigably as heretofore. 



It is my intention, with this prospect in view, to point 

 out in these columns some methods of research in study- 

 ing the fauna of the sea, which 1 believe will be of great 

 advantage to science. 



The manner in which the dredging of the sea is carried 

 on from a vessel is generally this. The deposit on the bot- 

 tom which the trawl or other similar appliance brings up 

 is carefully sifted, and its animal contents placed in suit- 

 able vessels filled with spirits or other fluid for preserva- 

 tion. If time serves, a sorting of the various objects takes 

 place at once, so that animals of various groups are de- 

 posited in separate vessels. These latter are either fully 

 marked or else simply ticketed with a number, which is 

 interpreted by an entry in the " dredging-log " kept for 

 that purpose. The object of this log is, in the first instance, 

 to fix exactly the spot — la'itude and longitude — where 

 the sample was taken, the time of the capture, the con- 

 dition of the bottom, the depth, the temperature of the 

 water, and if possible also the contents of salt both at 

 the depth from which the sample was taken and at 

 the surface. These are the annotations which have 

 up to the present time been made by scientists 

 when dredging. When the samples or collections 

 thus obtained reach terra Jinna their scientific examina- 

 tion commences, and it becomes a matter of great 

 moment to extract from these laboriously collected 

 fragments a scientific whole which will be of value to 

 zoology. The various groups of animals are consigned 

 to different hands, i.e. taken in hand by specialists, the 

 result of whose researches will naturally vary according 

 to the lines of study they pursue. In nearly every in- 

 stance the result of the same is a descriptive or anatomi- 

 cal work, as well as a work of the fauna ; varieties and 

 forms new to science are described, delineated, and 

 placed in their true position in the system, while some 

 previously known are shown to exist in places where they 

 had hitherto been unknown. Science has thereby made 

 a double gain, viz. a systematic and a zoogeographical. 



With regard to the systematic gain, it is no doubt consi- 

 derable. The descriptions, with or without illustrations, 

 may be long or short, and refer either to the exterior 

 forms or interior construction, i.e. its anatomy in a 

 limited sense ; still they are invariably fruitful if they are 

 only sufficiently complete and, what is of most conse- 

 quence, methodical. Both anatomy and morphology will 

 in most instances obtain from them what is demanded by 

 these sciences. But on the other hand the zoogeographi- 

 cal gain is very unsatisfactory. What do we thus, for 

 instance, learn from such a statement as this, that 

 Yoldia arctica has been met with in lat. 73 o' north, and 

 long 68° 15' east ? Nothing more nor less, in fact, than 

 that it has been found in this particular place along with 

 many others. By comparing, however, this locality with 

 the others where it has previously been found, 1 no 

 doubt gain a certain knowledge of its horizontal distri- 

 bution, but I do not in the least degree learn from this 

 statement the laws which govern the same. If, on the 

 other hand, I am informed that the bottom in the place 

 of discovery is brown sand mixed with clay, that the 

 depth is eight fathoms, that the temperature of the 

 water was —2° C. , and its specific weight 1 0273, I have 

 at once materials for a far wider knowledge. These par- 

 ticulars furnish me with a basis for ascertaining the ex- 

 ternal conditions which regulate the existence of this 

 species ; and if I, besides these particulars, also learn 

 with what animals of the same and other genus the 

 Yoldia has been found in that particular place, I obtain 

 a certain imperfect idea of the animal life existing 

 there. I said imperfect, as, in order that the description 

 should be complete, it is necessary I should also know 

 the number of each species found. If I had thus informa- 

 tion of how many individual Yoldia were taken in this 

 place, and how many of the other species of animals were 

 taken, and also if specimens of every one of the animals 

 existing in this place had come up in the trawl, then I 

 should possess an approximate knowledge of the animal 

 fauna existing in such a place. The knowledge of the 

 relative number of the species in a certain place is, in 

 my opinion, a factor of essential importance to the science 

 of zoogeography. 



The example I have just quoted shows sufficiently how- 

 very incomplete the zoogeographical statements are 

 which only record the exact place where certain species 

 were taken. On such a basis nothing of any scientific 

 value can be founded. 



It would, I consider, be of immense value to zoology if 

 dredgings during the larger expeditions were effected by 

 men skilled in every branch of this science. It is clear that 

 the more copious and varied the knowdedge of the zoolo- 

 gist is the greater will the gain be to science on this point, 

 especially if the student is able at the moment to take full 

 note of what is brought to the surface. If this be the 

 case, he would be able there and then to classify the 

 varieties caught and particularly record the number of 

 individuals taken, which is naturally of most consequence 

 where it is not possible to preserve all species. Such 

 records would be of great value to students of zoo- 

 geography, and I am under the impression that as yet no 

 zoologist has conceived this idea, or at all events not 

 carried it into execution. 



It would undoubtedly be a matter of some difficulty, from 

 the copiousness of the existing zoological literature, and 

 the consequent impossibility of mastering the same, to 

 find men who are experts in every branch of descriptive 

 zoology, and at the same time prepared for such work as I 

 have indicated here. While the mere mechanical act of 

 dredging must necessarily be effected by younger men, 

 the careful sifting of the deposit brought up is of such 

 importance that it should only be done by a zoologist of 

 advanced years and study ; but as it seems an impossi- 

 bility to combine the two conditions, the only possible 

 way out of the difficulty is for the zoologist to preserve all 



