1895. NOTES AND COMMENTS. 229 



practical suggestion is that, with the consent of ParHamentary and 

 local authorities, a royalty should be charged on any minerals obtained 

 below a certain depth, while landowners might defray a part of the 

 cost of borings upon their estates. 



Murray's Mud-line. 



In the Zoological Section, Professor Herdman discussed chiefly 

 problems of oceanography, problems with which his own great 

 experience in dredging rendered him specially familiar. After paying 

 a high compliment to Dr. John Murray, a compliment which must 

 have echoed in the minds of every naturalist who heard it, he 

 discussed at some length the existence of what Murray has called the 

 " Mud-line " around coasts at a depth of about one hundred 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 (Murray) 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." In fact, to 

 this region Murray assigned the importance that, it may be 

 remembered, Professor Moseley assigned to the shore generally. 



Professor Herdman thinks that the limits of the mud-region are 

 much more variable and its fauna much scantier than Murray's view 

 requires. " In the Irish Sea 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 current runs. A deposit of mud may be due to the 

 presence of an eddy or a sheltered corner in which the finer particles 

 suspended in the water are able to sink, or it may be due to the 

 wearing away of a limestone beach, or to quantities of alluvium 

 brought down by a stream from the land, or to the presence of a sub- 

 merged bed of boulder clay, or even, in some places, to the sewage 

 and refuse from coast towns. Finally, there is the deep-water mud, 

 a very stiff, blue-grey substance, which sets, when dried, into a firm 

 clay, and this is, I take it, the mud of which Dr. Murray writes. 

 But in none of these cases, and certainly not in the last-mentioned, is 

 there, in my experience, or in that of several other naturalists I have 

 consulted, any rich fauna associated with mud. In fact, I would 

 regard mud as supporting a comparatively poor fauna as compared 

 with other shallow water deposits." 



Dr. Herdman supported his view by a large quantity of evidence, 

 all of which went to show that the " Coralline " zone, and especially 

 the " Laminarian " zone, have much richer faunas than those of the 

 muddy regions. 



