34 PROCEEDINGS OF THE 



African coast, into tlie ^gean Sea and the Sea of Marmara. 

 This expedition thus entered upon the ground rendered classical 

 by Porbes half a century before. The results are in course of 

 publication in the Deukschr. Ak. Wiss. "Wien, and, to judge from 

 the portions which have appeared, seem to be quite in propor- 

 tion to the care with which this expedition has been planned 

 and fitted out. I find that the observatory stations must have 

 amounted to several hundreds, but in the reports published only 

 about 60 are referred to as having yielded Deep-sea material. 

 The greatest depth ascertained by the sounding-line in this part 

 of the Mediterranean is 2566 fathoms ; viz., in Lat. 35° 45', 

 Long. 21° 46' (Paris). 



Dr. E. von Marenzeller, who took part in the expedition and 

 has worked out the Echinoderms, is of opinion that, although it 

 is probable that the variety of Deep-sea life is numerically 

 diminished in the great depths, such inferiority is by no means 

 proved. He distinguishes three bathymetrical zones : — 1. The 

 littoral, from the surface to 170 fathoms ; 2, the continental, 

 between 170 and 580 fathoms ; and 3, the abyssal, from 580 

 fathoms downwards. He does not find a characteristic difference 

 between the Mediterranean and Atlantic faunae ; but the number 

 of littoral species descending into the continental and abyssal 

 zones, as well as the number of continental species descending 

 into the abyssal zone, is much greater in the Mediterranean than 

 in the Atlantic. He accounts for this by the uniformity of 

 a comparatively high temperature from the depth of a hundred 

 fathoms to the bottom, however distant from the surface this 

 may be. 



'ihe whole of the history of these explorations in the Mediter- 

 ranean seems to point to a lesser abundance of animal life in the 

 great depths than exists in the Atlantic. Although fitted out 

 with much better apparatus, none of the hauls of the last three 

 expeditions can compare with those grand captures made by the 

 dredge of the ' Porcupine,' and still less with those of the ' 'Talis- 

 man ' and the ' Challenger ' in the Eastern Atlantic. Possibly, in 

 certain limited localities conditions prevail causing an entire 

 absence of life. But such an azoic condition exists only in the 

 Black Sea, the deep water and the deposits being, as Russian 

 explorers have shown, unfit for life, owing to an enormous 

 accumulation of sulphides and sulphuretted hydrogen. 



The "Western North Atlantic. 



I include under this heading the work done in the Western 

 IS orth Atlantic, south of the Arctic area and north of about the 

 25° of N. Lat. 



The men at the head of the U.S. Coast Survey, especially 

 Professor Bache, showed a keen interest m the Biology of the 

 Deep Sea, and from the year 1850 we meet with papers treating 

 of the microscopical constitution of deep-sea soundings, notably 



