HISTORICAL DEVELOPMENT OF THE CONCEPT 15 



being drawn from the characteristic genus. The first of these exhibited 

 several neritic subtypes in the seas about the British Isles and Den- 

 mark. In an estimate of Cleve's work, Gran points out certain diffi- 

 culties (1912:359), but concludes that it yields a biological grouping 

 that is satisfactory in the main. 



By means of seven or eight samples throughout the year in the 

 same general area, Cleve was enabled to follow the changes in the 

 abundance of diatoms and cilioflagellates in particular. These swarms 

 or pulses correspond in several particulars to the aspects exhibited by 

 land biomes. 



Petersen and Associates (1911-1925). The first organization of 

 the animal communities of the sea bottom was carried out by Petersen 

 (1913, 1914, 1918), as a by-product of the quantitative study of fish 

 food in different areas. Certain species predominated in the bottom 

 samples with such regularity that it proved possible not merely to 

 recognize eight animal communities from the deep water of the Skager- 

 rack to the Baltic, but actually to indicate the distribution of these 

 on a chart of the region. (See Fig. 84, p. 349.) He clearly perceived 

 the great differences between the various groupings and utilized a 

 synoptic method of characterizing these by means of the prevalent 

 animals. The conclusion was drawn that the Macoma community 

 occurred throughout in the shore zone, the Venus community with 

 certain spatangids on sandy bottom in deeper waters, Brissopsis and 

 its associates on soft clay outside these, and other communities in still 

 deeper water. 



This classic series of quantitative investigations was centered on 

 the food coactions from producent to consument and upon the compo- 

 sition and distribution of the bottom communities. The first mono- 

 graph, by Petersen and Jensen (1911), dealt with the animal life of 

 the sea bottom, its food and quantity; the second discussed the cor- 

 responding animal communities and their importance for marine zoo- 

 geography (Petersen, 1913). A third report (1914) discussed in 

 greater detail the organic matter of the bottom (Boysen Jensen) , and 

 also described the food and conditions of nutrition for the invertebrate 

 communities in Danish waters (Blegvad) , a theme further elaborated 

 by the latter in 1916. Two years later, Petersen (1918) made a com- 

 prehensive account of the so-called valuation studies of the preceding 

 decade, and in 1925 Blegvad gave further data upon the relations of 

 the dominant fishes to the invertebrate communities. 



Murray and Hjort (1912). In the "Depths of the Ocean," Murray 

 and Hjort have presented an invaluable summary of oceanography, 

 from what is in some respects essentially a bio-ecological viewjioint. 

 The lack of contact between ecology and oceanography at that time 

 serves to explain in part the absence of a definite and comprehensive 

 account of the biotic communities and their relations, though this is 

 due even more to the enormous number of organisms considered and 

 the necessity of treating various great groups from the standpoint of 

 the specialist. In spite of this, the book constitutes the nearest ap- 

 proach to an actual organization of the pelagic communities in the 

 ocean and supplies a vast amount of data for ecological analysis and 



