THE PROBLEMS OF THE DEEP SEA. 455 



In the course of the dredging of the Porcupine, it was frequently- 

 found that, while few objects of interest were brought up within the 

 dredge, many living creatures came up sticking to the outside of the 

 dredge-bag, and even to the first few fathoms of the dredge-rope. 

 The mouth of the dredge doubtless rapidly filled with mud, and thus 

 the things it should have brought up were shut out. To remedy this 

 inconvenience Captain Calver devised an arrangement not unlike that 

 employed by the coral-fishers. He fastened half a dozen swabs, such 

 as are used for drying decks, to the dredge. A swab is something like 

 what a birch-broom would be if its twigs were made of long, coarse 

 hempen yarns. These dragged along after the dredge over the surface 

 of the mud, and entangled the creatures living there multitudes of 

 which, twisted up in the strands of the swabs, were brought to the sur- 

 face with the dredge. A further improvement was made by attach- 

 ing a long iron bar to the bottom of the dredge-bag, and fastening 

 large bunches of teased-out hemp to the end of this bar. These 

 " tangles " brought up immense quantities of such animals as have 

 long arms, or spines, or prominences which readily become caught in 

 the hemp, but they are very destructive to the fragile organisms which 

 they imprison ; and, now that the trawl can be successfully worked at 

 the greatest depths, it may be expected to supersede them ; at least, 

 wherever the ground is soft enough to permit of trawling. 



It is obvious that between the dredge, the trawl, and the tangles, 

 there is little chance for any organism, except such as are able to 

 burrow rapidly, to remain safely at the bottom of any j>art of the sea 

 which the Challenger undertakes to explox-e. And, for the first time 

 in the history of scientific exploration, we have a fair chance of learn- 

 ing what the population of the depths of the sea is like in the most 

 widely-different parts of the world. 



And now arises the next question. The means of exploration be- 

 ing fairly adequate, what forms of life may be looked for at these vast 

 depths ? 



The systematic study of the Distribution of living beings is the 

 most modern branch of Biological Science, and came into existence 

 long after Morphology and Physiology had attained a considerable 

 development. This naturally does not imply that, from the time men 

 began to observe natural phenomena, they were ignorant of the fact 

 that the animals and plants of one part of the world are different from 

 those in other regions ; or that those of the hills are different from 

 those of the plains in the same region ; or, finally, that some marine 

 creatures are found only in the shallows, while others inhabit the 

 deeps. Nevertheless, it was only after the discovery of America that 

 the attention of naturalists was powerfully drawn to the wonderful 

 differences between the animal population of the central and southern 

 parts of the New World and that of those parts of the Old World which 

 lie under the same parallels of latitude. So far back as 1667 Abraham 



