OCEANOGRAPHY, BIONOMICS, AND AQUICULTURE. 439 



temerity in venturing to differ from one who has had such an extended 

 experience of the sea and its problems, 1 am constrained to express 

 my disagreement with some of his conclusions. And I am encouraged 

 to do so by the belief that Murray will rightly feel that the best compli- 

 ment which zoologists can pay to his work is to give it careful, detailed 

 consideration, and discuss it critically. He will, I am sure, join me in 

 the hope that, whether his views or mine prove the false ones, Ave may 

 be able, by their discussion, to close a "path toward error," and possi- 

 bly open " the road to truth." 



One of the points upon which Murray lays considerable stress, and 

 to the elaboration of which he devotes a prominent position in his 

 "General observations on the distribution of marine organisms,''' is the 

 presence of what he has called a "mud-line" around coasts at a depth 

 of about 100 fathoms. It is the point "at which minute particles of 

 organic and detrital matters in the form of mud begin to settle on the 

 bottom of the ocean." He regards it as the great feeding ground, and 

 a place where the fauna is most abundant, and from which there have 

 hived off, so to speak, the successive swarms or migrations which 

 have peopled other regions — the deep waters, the open sea, the shallow 

 waters and the estuaries, fresh waters, and land. Murray thus gives 

 to his mud-line both a present and an historic importance which can 

 scarcely be surpassed in the economy of life on this globe. I take it 

 that the historic and the present importance stand or fall together — 

 that the evidence as to the origin of faunas in the past is derived from 

 their distribution at the present day, and I am inclined to think that 

 Murray's opinion as to the distribution of animals in regard to the 

 mud-line is not entirely in accord with the experience of specialists, 

 and is not based upon reliable statistics. Murray's own statement is 

 {Challenger Expedition, Summary, Vol. II, p. 1433): "A depth is 

 reached along the continental shores facing the great oceans immedi- 

 ately below which the conditions become nearly uniform in all parts of 

 the world, and where the fauna likewise presents a great uniformity. 

 This depth is usually not far above nor far below the 100-fathom 

 line, and is marked out by what I have elsewhere designated as the 

 Mud-line. - - - Here is situated the great feeding ground in the 

 ocean - - - " and he then goes on (p. 1434) to enumerate the Crusta- 

 ceans, such as species of Calanus, JEuchceta, PasipJuva, Crangon, Calocaris, 

 Pandalus, Hippolyte, many amphipods, isopods, and immense numbers 

 of schizopods, which swarm, with fishes and cephalopods, immediately 

 over this mud deposit. Now, I venture to think that the experience of 

 some of those who have studied the marine zoology of our own coasts 

 does not bear out this statement. In the first place, our experience in 

 the Irish Sea is that mud may be found at almost any depth, but is very 

 varied in its nature and in its source. There may even be mud laid 

 down between tide marks in an estuary where a very considerable cur- 

 rent runs. A deposit of mud may be due to the presence of an eddy 



