The fishes of the Danmark Expedition. 643 



Sertularella gigantea, Thujaria laxa). Here we find among other 

 things numerous coral-like colonies of Bryozoa, and from these I 

 have called this region the "coral bottom". At some places it is 

 also met with at 300 m, replaced here and there b}^ bare sand and 

 gravel banks as in the hydroid region. 



We may turn now from the hard bottom to the corresponding 

 conditions on the soft bottom. This is found for example 

 over the greater part of Danmarks Havn, the coasts here being 

 for the most part raised sea-bottom in the form of level sand, 

 gravel or clay plains; and these continue out under the water, so 

 that the depth increases slowly. At several places water-courses 

 flow out into the harbour (or have done so) and the material 

 brought down by these contributes by deposition to level up and 

 cover the bottom with a soft layer. Regarded as a whole the 

 littoral region at these places has a very poor vegetation; there 

 is even no vegetation at all over wide areas, especially sandy areas, 

 but in the shelter of large stones we find a few Fucus, or masses 

 of sea-weed (especially stumps of Laminaria, Chlorophyceae etc.) 

 lie here and there (especially in the bays). This applies in still 

 higher degree to the Laminaria region, as the amount of loose algae 

 is often greater than the quantity of the fixed (in contrast to the 

 hard bottom), and in less degree to the succeeding Delesseria region. 

 Off" the larger rivers the vegetation of algae is poorest, probably 

 owing to the large quantity of fresh water and the constant deposi- 

 tion of sand; often however we find here the washed-out remains 

 of moss and other freshwater and land plants, especially when the 

 rivers begin to flow. A true littoral, algal vegetation is thus wanting 

 here, and the Laminaria region also begins further out (ca. 10 m) 

 than elsewhere. This region also has its main distribution about 

 10 m, beginning usually at 5 m (if there is but one loose stone, to 

 which the algae can attach themselves to) and it extends out to ca. 

 15 m, at places even to ca. 20 m (where the water is specially clean). 

 At the latter depth it changes over into the Delesseria region, 

 which is characterized by red algae (mentioned on p. 642), and these 

 beautiful foliaceous algae also attain here a much greater distribu- 

 tion than on the corresponding Lithotamnion region. The calcareous 

 algae, on the other hand, are scarcer here, being more numerous 

 the more the bottom-soil approaches to the hard bottom (stones, 

 shells). This red-algae region extends out to very deep water on 

 the soft bottom, the algal vegetation gradually becoming scarcer; 

 a hydroid and coral region are wanting naturally with the stones. 

 The Delesseria region has its typical form at ca. 20 m and extends 

 out to ca. 50 m. Beyond this depth we might perhaps set up a 



