FIRST FOUR DECADES OF THE TWENTIETH CENTURY 



ulations; The Biology of Death (1922) and 

 Studies in Human biology (1924), dealing 

 with human populations. Lotka's Elements 

 of Physical Biology (1925) covered certain 

 phases of biotic interactions from a rational, 

 theoretical viewpoint, and, as its meaning 

 is slowly assimilated, becomes an increas- 

 ingly distinguished contribution. 



In the field of human ecology, stiaddUng 

 the fence between biology and sociology, 

 two books by Ellsworth Huntington came 

 out (Principles of Human Geography, 1921, 

 with Gushing; Civilization and Climate, 

 1924), along with The Population Problem, 

 by Carr-Saunders in 1922, and Der Gang 

 der Kultur iiber die Erde, by Hettner in 

 1923. 



A rapidly advancing field during the 

 twenties was paleo-ecology. Although the 

 plant ecologists were most concerned, there 

 were enough general principles emerging 

 to warrant the attention of animal workers. 

 Paleo-ecology may lack the quantitative 

 methods of modern ecology, but it is a 

 necessary approach if evolutionary views 

 are to be applied outside taxonomic and 

 phylogenetic studies. A direct way to study 

 this subject by means of modern geological 

 structures was carried out by Professor 

 Richter and his associates in the Sencken- 

 berg Museum in Frankfurt. A convenient 

 English summary of this method was pub- 

 lished by Bucher in 1938. Other significant 

 publications were F. Clements' (1924) 

 Methods and Principles of Palaeo-ecology; 

 O. Abel's (1929) Paldobiologie und Stam- 

 mesgeschichte, and a summarizing paper in 

 the next decade (1935) by C. L. Fenton 

 entitled "Viewpoints and Objects of Paleo- 

 ecology." In 1928 a journal, "Palaeobiolo- 

 gica," edited by Abel, was founded and 

 published in Vienna. 



The general ecology texts by Pearse and 

 Elton warrant further examination. They 

 show how two specialists organized ecology 

 during the third decade. Pearse had the 

 following chapter headings: 



1. Introduction, ii. Physical and chemical 

 ecological factors, iii. Biological factors, iv. 

 Succession, v. Animals of the ocean, vi. Fresh- 

 water animals, vii. Terrestrial animals, viii. The 

 relations of animals to plants, ix. The relations 

 of animals to color, x. Intraspecific relations, xi. 

 The economic relations of ecology. 



He thus laid a general background of phys- 

 ical and biotic factors and then classified 

 animals ecologically according to their major 



Oi 



habitats. The treatment was primarily 

 descriptive. 



Elton's book appeared under the spon- 

 sorship of Julian S. Huxley, who said in 

 the Forewor-^' ^p. xiii) : 



"Finally, there remain subjects which are of 

 such recent growth that their principles have 

 never yet been treated in a comprehensive way. 

 Such, for instance, are developmental and com- 

 parative physiology, animal behaviour and 

 ecology. From the point of view of the rapid 

 growth and expansion of general biology, it is 

 these subjects which it is at the present 

 moment most important to summarise in brief 

 text-books, since otherwise the multifarious 

 knowledge which we have already attained re- 

 garding them remains locked up in scattered 

 papers, the property of the specialist alone. 

 The present volume deals with a much mis- 

 understood and often underrated subject." 



The emphasis that Elton placed on ecol- 

 ogy was different from that of Pearse, as 

 was the manner of treatment. This can be 

 seen from the following table of contents: 



i. Introduction, ii. The distribution of animal 

 communities, iii. Ecological succession, iv. En- 

 vironmental factors. V. The animal community, 

 vi. Parasites, vii. Time and animal communities, 

 viii. The numbers of animals, ix. Variations in 

 the numbers of animals, x. Ecological methods, 

 xi. Ecology and evolution. 



Elton was concerned more with organiz- 

 ing ecology around principles, and most of 

 his principles centered around the animal 

 community and the natural population. Un- 

 hke Pearse, he was interested, not so much 

 in whether an animal was found in a desert 

 or a lake, but rather in the environmental 

 factors hmiting the distribution of such a 

 form. Elton stressed also the quantitative 

 aspects, particularly in connection with the 

 number of animals that occupy any com- 

 munity and the impact that these numbers 

 make on their total environment. He viewed 

 food chains as the most important integrat- 

 ing factor of the community, and his treat- 

 ment of this subject is outstanding. 



As we view the growing organization of 

 ecology during the period 1921 to 1930, 

 it looks something hke this. There was a 

 rough dichotomy between the physical- 

 chemical environment and the biotic envi- 

 ronment. The former was broken down into 

 a series of factors of greater or lesser eco- 

 logical significance that were studied as 

 "conditions of existence." This was a phrase, 

 apparently tracing back to Karl Semper 



